Ceratozamia norstogii: Identifying Animals which disperse the seeds of an Endangered Mexican Cycad.

The genus Ceratozamia comprises about 35 species of neotropical Cycads, all but one of which are found only in Mexico. As such they form an important part of Mexico's botanical diversity, and understanding their ecology and evolutionary history is seen as a key to understanding the climatic history of northern Mesoamerica. 

One of the major steps in understanding the biogeography of any Plant is working out how its seeds are dispersed. This is particularly challenging for Cycads, as their seeds tend to be rather large, and often contain methylazoxymethanol glycosides, which are toxic to most Vertebrates. Nevertheless, most Cycad seeds are thought to be dispersed largely by Rodents and other small-to-medium sized Mammals. 

The seeds of members of the genus Ceratozamia are thought to be particularly toxic, and are therefore presumed to be dispersed largely by gravity. However, this theory has never been put to the test, and it is hard to explain the wide distribution of the genus through gravitational seed dispersal alone.

In a paper published in the Biodiversity Data Journal on 24 August 2022, Héctor Gómez-Domínguez of Senda Sustentable, and Jessica Hernández-Tapia and Andrés Ortiz-Rodriguez of the Departamento de Botánica at the Universidad Nacional Autónoma de México, present the results of an experiment in which two specimens of Ceratozamia norstogii in La Sepultura Biosphere Reserve in Chiapas State, Mexico, were observed by camera trap for ten months in order to assess what Animals were feeding on and spreading their seeds.

Ceratozamia norstogii in the study area. On the left, Plant in reproductive phase (prepollination). Top right, habitat (Pine-Oak forest). On the bottom right, a seedling growing amongst the leaf litter. Héctor Gómez Domínguez & Ana Rocha in Gómez-Domínguez et al. (2022).

Ten months is the time taken from the first appearance of the cones of Ceratozamia norstogii until their disintegration. The cones in La Sepultura Biosphere Reserve were observed over this cycle between October 2020 and July 2021. The first seven months of the growth cycle, October-April, were taken up by the pre-pollination growth phase, during which time the cone reaches its maximum size. The second phase lasts around two months, May-June, and is where pollination occurs. During this phase the cones exude a sweet smelling, amber-coloured liquid which attracts Beetles of the Family Erotylidae (Pleasing Fungus Beetles), known to be important pollinators of Cycads. During the final phase, from June to August, the seeds mature to a brown colour, and are either carried away or eaten by frugivorous Animals, or fall to the ground as the cone disintegrates. 

Female cone maturation. Pre-pollination phase. (A) Emergent cone, with a short, straight peduncle and a general reddish-brown colouration. (B) Young cone, a larger brown cone with a straight peduncle. (C) A large, fully developed cone with a greenish colouration, peduncle much longer and bent towards the ground. Pollination phase. (D) A large, pendant cone, with a light brown colouration, and barely separation amongst megasporophylls. Seed maturation phase. (E) A large, pendant cone, with a light brown colouration and with an evident separation amongst megasporophylls. (F) Mature seeds. Ana Rocha in Gómez-Domínguez et al. (2022).

During the whole ten months, seven Animals were recorded visiting the female cones, the majority of them at night. The daytime visitors comprised three Birds of different species who used the cones as perches during the daytime; two during the immature growing phase, and one while a cone was disintegrating. Also during daylight hours, a Badger was seen to approach a cone, pausing to smell it before leaving. 

During the night, several small-to-medium sized Mammals both visited and interacted with the cones. Most notably, a Mouse of the genus Pteromiscus was observed both feeding on the exudate of the cones, and removing seeds and carrying them beyond the range of the camera, on several occasions. A Kinkajou, Potus flavus, was also seed removing seeds from the cones, although it appeared to be doing this in order to access the central axis of the cone, which it spent some time biting. This is a significant observation for the Kinkajou, a small Mammal usually presumed to live and feed almost exclusively within the tree canopy, but which approached the cone from the ground, but does not appear to have aided the distribution of the Cycad's seeds. Finally, a Southern Spotted Skunk, Spilogale angustifrons, was again observed to bite at the seeds and carry several beyond the reach of the camara.

Female cone visitors of Ceratozamia norstogii. (A) Mouse, Pteromiscus sp., collecting seeds; (B) Southern Spotted Skunk, Spilogale angustifrons, biting the cone and collecting seeds; (C) Kinkajou, Potus flavus, removing seeds. Gómez-Domínguez et al. (2022).

Three species of frugivorous Mammal were observed visiting the cones of Ceratozamia norstogii, all of them at night (after 8.00 pm), with most of the activity happening between 12.00 midnight and 3.00 am. This activity peaked in the second week of July, but carried on for 20 nights, during which time the cones were visited on 65% of nights. The Mouse was the most common visitor, visiting the cone on 13 nights, and making a total of 40 visits. The Southern Spotted Skunk made 15 visits on 3 nights, while the Kinkajou made two visits on a single night. Based upon this, Gómez-Domínguez et al. conclude that the Mouse, Pteromiscus sp., is the most effective distributor of the seeds of Ceratozamia norstogii.

Gómez-Domínguez et al.'s results support the hypothesis that the seeds of Ceratozamia norstogii are distributed by small-to-medium sized Mammals, with the Mouse, Pteromiscus sp., being the most effective distributor. The other two species were less frequent visitors, and were probably feeding opportunistically, rather than using the cones as a regular seasonal food resource. Both are primarily insectivorous, but are also secondarily omnivorous, feeding on smaller Animals, carrion, and fruit. The feeding activity of the Kinkajou was particularly surprising, given that the activities of this Animal are usually restricted to the treetops, but probably not significant for the Cycad. The Southern Spotted Skunk, on the other hand, could potentially be an occasional important seed disperser for this Plant, given that it has a much greater home range than the Mouse, making it likely to carry the seeds for greater distances.

The finding that the seeds of Ceratozamia norstogii are distributed by only a small number of species is consistent with other studies of Cycads, whose seeds are typically dispersed by a small number of, or even a single, species. This contributes to the distribution seen in Cycads, which tend to be found in fairly dense colonies, where it is hard to distinguish between gravity dispersed seeds and seeds dispersed by small Mammals who only carry them a few metres.

This short-distance dispersal is likely to have promoted allopatric speciation (the division of colonies into new species after they become geographically isolated) within the genus Ceratozamia. Within this genus, episodes of speciation appear to have been linked to extinction events in which clades of large Mammals disappeared. This could potentially suggest that the seeds have historically been dispersed over long distances by a variety of large Mammals, but that when these species have gone extinct this role has fallen to smaller Mammals with limited ranges, effectively cutting off the widely dispersed colonies from one-another.

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Vishnuonyx neptuni: A new species of Otter from the late Miocene Hammerschmiede Fauna of Bavaria.

The Hammerschmiede locality in Bavaria, Germany, has been producing Late Miocene Vertebrate and Invertebrate fossils for almost five decades. The fossils are predominantly found within a series of river channels, and date to between 11.62 and 11.44 million years ago. Over 130 species of Vertebrate have been recorded from this location, several of which are unknown from any other location, most notably the Ape, Danuvius guggenmosi. Despite this high diversity, to date only two species of Carnivorans have been described from Hammerschmiede, the Palm Civets Semigenetta sansaniensis and Semigenetta grandis. 

In a paper published in the Journal of Vertebrate Palaeontology on 16 September 2021, Nikolaos Kargopoulos of the Department of Geosciences at Eberhard Karls University of Tübingen, Alberto Valenciano of the Departamento de Ciencias de la Tierra, and Instituto Universitario de Investigación en Ciencias Ambientales de Aragón at the Universidad de Zaragoza, Panagiotis Kampouridis, also of the Department of Geosciences at Eberhard Karls University of Tübingen, and Thomas Lechner and Madalaine Böhme, also of the Department of Geosciences at Eberhard Karls University of Tübingen, and of the Senckenberg Centre for Human Evolution and Paleoenvironment, describe a new species of 'Bunodont' Otter from the Hammerschmiede locality.

The phylogeny and classification of Otters, Lutrinae, is generally poorly resolved, with the relationship of fossil groups such as the Potamotheriinae and Bunodonts to modern Otters remaining unclear. Bunodont Otters are a (probably paraphyletic) group of large and very large fossil Otters found across Eurasia, Africa, and North America. The classification of this group is itself poorly resolved, with uncertainty about which fossils should be included within it, with one genus, Enhydrictis, having been recently reclassified and no longer thought of as an Otter at all. 

The new species is placed in the genus Vishnuonyx, which contains previously described species from the Miocene of South and Southeast Asia and the Miocene and Pliocene of Africa, and given the specific name neptuni, in reference to Neptune, the Roman god of the seas. The species is described from a right hemimandible, with a first premolar alveolus (canine tooth socket) and the second, third and fourth premolars and first molar intact. A left hemimandible and a number of isolated teeth are also referred to the species. All were recovered from river channel deposits at Hammerschmiede between 2011 and 2020, during excavations carried out by palaeontologists from Eberhard Karls University of Tübingen.

 

The lower dentition of Vishnuonyx neptuni. (A) SNSB-BSPG 2020 XCIV-0301, right hemimandible (holotype; original specimen and screenshots of its 3D model) in labial (A1), (A4), lingual (A2) and occlusal (A3) views; (B) GPIT/MA/16733, left hemimandible in labial (B1), lingual (B2), (B4) and occlusal (B3(, (B5) views; (C) SNSB-BSPG 2020 XCIV-1301 right p4 in labial (C1), lingual (C2) and occlusal (C3) views. Screenshots of the 3D models not in scale. Kargopoulos et al. (2021).

The third premolar of Vishnuonyx neptuni is distinctly asymmetrical, with the bak of the tooth being visibly lager than the front. The main cusp has three crista (ridges) deriving from it, one at the front, one at the back, and one on the inside edge. The inside crysta expands to form part of the wall of the tooth, which hosts one of the three roots of the tooth.

The upper carnassial tooth (front molar, modified to have a cutting edge which occludes the cutting edge on the lower tooth, a diagnostic trait of Carnivorans) has moderate wear on its cutting edge. The tooth has a strong cingulum (convex protuberance below the crown). The tooth has a high paracone (front outer) cusp, which is attached to a ridge a metastyle (ridge on the outer surface). There is no carnassial notch (notch used to hold bone for a crushing bite, a common Carnivoran trait). The protocone, parastyle, and paracone cusps form a line, with the hypocone outside this, behind the paracone. 

 

The upper dentition of Vishnuonyx neptuni. (A) SNSB-BSPG 2020 XCIV-1022, left P3 in occlusal (A1), labial (A2) and lingual (A3) views; (B) GPIT/MA/17347, right P4 (original specimen and screenshots of its 3D model) in occlusal (B1), (B4), labial (B2), (B5) and lingual (B3), (B6) views; (C) SNSB-BSPG 2020 XCIV-1552, left M1 (original specimen and screenshots of its 3D model) in occlusal (C1), (C4), labial (C2), lingual (C3), mesial-occlusal (C5) and mesial (C6) views. Abbreviations: meta, metacone; metal, metaconule; lp, lingual platform; para, paracone; paral, paraconule; prot, protocone; protl, protoconule. Kargopoulos et al. (2021).

The upper molar is complete with some wear to the inner sides of the paracone and metacone. A distinct cingulum is present, although this is less developed towards the forepart of the toorh. The tooth is nearly rectangular in outline, and somewhat slim, although the outer suface is slightly higher at the fore than at the rear. The inner cusps are roughly the same height, and connected by a low crest with a notch towards its middle. Behind these two further cusps, the protoconule and metaconule rear cusps are connected by another ridge.

Neither of the two hemimandibles is complete. The right specimen preserves part of the socket of the canine, part of the angular process (bottom part of the back of the jaw) and part of the masseteric fossa (muscle attachment above the angular process), and everything in between. The muscle attachment is deepest at the top, the hind part of the hemimandible bent inwards, and the angular process small and hook-like. The left mandible is less well preserved, with only part of the canine socket, the cheek teeth and part of the masseteric fossa muscle attachment, however, on this specimen the attachments for the masseter pars superficialis and pars profunda muscles can be seen.

The canine is absent in both hemimandibles. The second premolar is two-rooted and has a distinct cingulum (convex protuberance beneath the crown), particularly on the inner side and towards the rear. The long axis of this tooth is not in line with the long axis of the tooth row. The third and fourth premolars are high and pointed, with their largest cusps towards the middle and inclined backwards. In the third premolar only a single cusp is present, and the tooth has a wrinkled surface. The fourth premolar is taller than the third (and the first molar), and has a second, smaller cusp behind the first. The first molar is broad, with a talonid (crushing region) covering about a third of its surface. The first cusp is wider than this crushing area. This tooth also has wide cingulum. 

The dentition of Vishnuonyx neptuni differs considerably from that of modern Otters, but fits well with the genus Vishnuonyx, which has been confidently assigned to the group based upon more complete material. This genus has previously been described from Asia and Africa, with the Asian specimens being older and less robust than the African specimens; Vishnuonyx neptuni, the first described European member of the genus, appears to be intermediate between these groups in both age and size.

 

Temporospatial distribution of the known species of the genus Vishnuonyx. Kargopoulos et al. (2021).

The oldest known member of the genus, Vishnuonyx maemohensis, comes from Mae Moh in Thailand, and is dated to the Middle Miocene, between 14.2 and 13.2 million years old. Slightly younger is the late Middle Miocene Vishnuonyx chinjiensis from the Siwalik Hills of northwest India, which is thought to be between 13.8 and 12.7 million years old. A second specimen assigned to Vishnuonyx chinjiensis has been described from Ngorora in western Kenya, this specimen being about 12 million years old. Also known from Africa is the Latest Miocene Vishnuonyx? angololensis from Lower Nawata in Lothagam, near the southwestern shores of Lake Turkana, Kenya, which is dated to between 7.3 and 6.6 million years ago. Finally, an Early Pliocene specimen Vishnuonyx sp. has been recorded from Ethiopia and is thought to be between 5.2 and 4.85 million years old. The HAM 4 fossiliferous layer at Hammerschmiede, which produced Vishnuonyx neptuni, has been dated to 11.44 million years ago, making Vishnuonyx neptuni slightly younger than Vishnuonyx chinjiensis.

This suggests that the genus Vishnuonyx originated in Southeast Asia, and migrated westwards through the Indian subcontinent, reaching Europe and East Africa by the end of the Middle Miocene, with the genus persisting in East Africa into the Pliocene. Vishnuonyx neptuni is sufficiently different from other members of the genus to imply a reasonably long period of reproductive isolation, leading Kargopoulos et al. to reason that its ancestors reached Europe before 11.5 million years ago.

Vishnuonyx is thought to have had a semi-aquatic lifestyle similar to that of modern Otters, suggesting that it is most likely to have dispersed from Southeast Asia into South Asia, Europe, and Africa, by water. During the Middle Miocene the Central Paratethys Ocean separated East Africa and Arabia from southern Asia, with the Eastern Paratethys, separated from the Cenral Paratethys by the Araks Straight, forming a connection with Central Europe. This would have provided a plausible route for the westward expansion of the genus Vishnuonyx.

 

The proposed dispersal path of Vishnuonyx from South Asia towards Central Europe and East Africa during the Konkian around 13 million years ago (late Badenian, early Serravalian). Kargopoulos et al. (2021).

The teeth of Otters are adapted for two slightly different diets; catching slippery Fish, and breaking open hard shells. All living Otters pursue both these feeding methods to some extent, although they vary in the extent to which they depend on each method, which is reflected in their dental morphology. In species which primarily feed on hard-shelled prey such as Clams or Crustaceans, the molars tend to be broad and flat with well-developed crushing areas, whereas those that specialise in catching Fish tend to have high pointed cusps useful for catching slippery prey. The teeth of Vishnuonyx neptuni are apparently more adapted towards a piscivorous diet, with high, pointed premolars and a strong cutting blade on the molar. This is at odds with other 'Bunodont' Otters, which appear to have been primarily durophages specialising in hard prey, and suggests an ecology similar to that of the modern Amazonian Giant Otter, Pteronura brasiliensis.

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Populations of small Carnivores are becoming homoginised in the Niger Delta.

Carnivores are indicative of ecosystem health and integrity, and can potentially affect food web and community structure of lower trophic levels. Several studies of sympatric African Carnivore species have demonstrated that ecological separation is primarily related to dietary differences. As specialisation and resource selectivity is generally stronger in small carnivores than large ones, they may serve as useful indicator species of the state of an ecosystem. Thus, understanding the changes taking place in the assemblage and abundance of carnivores may allow the determination of the state of conservation of a particular habitat.

In a paper published in the African Journal of Ecology on November 2019, Glorious Onuegbu and Godfrey Akani of the Department of Animal & Environmental Biology at Rivers State University of Science and Technology, Luca Luiselli, also of the Department of Animal & Environmental Biology at Rivers State University of Science and Technology, and of the Institute for Development, Ecology, Conservation and Cooperation, and the Department of Zoology at the University of Lomé, Fabio Petrozzi of Ecologia Applicata Italia, Daniele Dendi also of the Department of Animal & Environmental Biology at Rivers State University of Science and Technology, the Institute for Development, Ecology, Conservation and Cooperation, and the Department of Zoology at the University of Lomé, John Fa of the Division of Biology and Conservation Ecology at Manchester Metropolitan University, and the Center for International Forestry Research, and Adaobi Ugbomeh and Ibiso Georgewill, again of the Department of Animal & Environmental Biology at Rivers State University of Science and Technology, describe the results of a study of small Carnivore diversity in the Niger Delta based upon animals being sold in bushmeat markets.

In the Niger Delta, members of four small carnivore families: Mustelidae (Weasels, Badgers, Otters, etc.) of which ther are two species, Viverridae (Civets and Genets), also two species, Nandiniidae (African Palm Civits), one species, and Herpestidae (Mongooses), three species. All are found in forest and forest‐derived habitats in the region. However, knowledge of their biology is still poorly understood primarily because of their secretive and nocturnal habits.

Small Carnivores are regularly consumed as bushmeat and sold in markets in West and Central Africa. Using records of species and individuals of small Carnivores sold in bushmeat markets, it is possible not just to uncover noteworthy aspects of their biology, but also determine whether hunting may be causing biotic homogenisation within the catchment supplying the markets. Onuegbu et al. use data from three markets in the surroundings of the city of Port Harcourt in Rivers State (Niger Delta, Nigeria) to evaluate whether a biotic homogenisation process on taxonomic, species richness diversity characteristics and perhaps substitution of species has occurred. They also compare their results with data from other markets in the same area and from other sites in southern Nigeria and neighbouring Benin Republic.

The study was carried out in the Rivers State, Nigeria. Rivers State has over 5 million inhabitants and a density of more than 630 persons/km². During the last 30 years, agricultural and industrial expansion throughout the region has caused severe fragmentation of the existing forests. The study area's climate is characterised by a long rainy season from April through to the end of September.

Map of Rivers State in southern Nigeria, showing the three sample stations. Onuegbu et al. (2019).

Onuegbu et al. monitored three bushmeat markets: Omagwa, Oyigbo and Mbiama. These study stations were chosen because they represent localities in which hunting, alongside traditional agriculture, provide important economic revenues for the resident rural population. These localities differ in terms of vegetation cover and human population density; the latter being significantly higher in Mbiama than in the other localities. Hunters living in bushland and forest patches, often more than 7 km away from the market, regularly supply a variety of animal carcasses for their sale.

In this study, Onuegbu et al. made the implicit assumption that small Carnivore abundance in bushmeat markets can be used as a proxy of small Carnivore abundance in the field. They surveyed bushmeat markets during the dry season (December 2017–March 2018) and in the wet season (May 2018–August 2018). Sampling effort was identical in the three market sites; they visited each market three times per week during 8 months (48 daily visits in each season). During each sampling day, Onuegbu et al. counted all animal carcasses on sale, including small Carnivores. All markets were visited between 7.00 am and 11.00 am, in order to be able to count and inspect carcasses as hunters dropped them with the bushmeat traders, and before traders dressed these (burning off the hairs/fur and butchering) making it more difficult to identify the species.

A total of 1206 carcasses of small Carnivores were recorded in the three study markets. The largest number (699) was observed at the Omagwa market, followed by Oyigbo (416) and Mbiama (91).

Onuegbu et al. recorded four different taxa, all Least Concern in the International Union for the Conservation of Nature's Red List of Threatened Species: the Flat‐headed Kusimanse, Cṛossarchus platycephalus, a member of the Herpestidae (1176), African Civet, Civettictis civetta (21), African Palm Civet, Nandinia binotata (6) and Genets, Genetta spp., possibly Genetta maculata (3). In all three markets, Cṛossarchus platycephalus accounted for over 97% of the total number of observed individuals, and the relative frequency of occurrence of the various species did not vary significantly among study areas.

The four observed small Carnivores: (a) Civettictis civetta (from Omagwa), (b) Genetta sp. (from Oyigbo), (c) Crossarchus platycephalus (from Omagwa) and (d) Nandinia binotata (from Omagwa). Onuegbo et al. (2019).

The number of carcasses was higher in the wet season than in the dry season, independently of the market and species. The increase in the number of traded carcasses from the dry months to the wet months was smooth and regular in the Oyigbo market, whereas numbers varied significantly in the other two markets. The number of carcasses was significantly positively correlated with monthly rainfall in all study markets.

Sex ratios were significantly skewed towards females in both Cṛossarchus platycephalus and Civettictis civetta, but sample sizes in Nandinia binotata and Genetta spp. were to small to assess. For Cṛossarchus platycephalus, the same female biased sex ratio was observed during both the dry and the wet seasons.

The basic premise of Onuegbu et al.'s study is that because hunters do not specifically target small Carnivores, the numbers appearing in the markets reflect their relative abundance in the market catchment areas. Using this data, they conclude that there is evidence that biotic homogenisation and species substitution is occurring in the eastern Niger Delta region.

Ongoing homogenisation process has already been shown for Snakes and Chelonians. Similarly, Onuegbu et al. demonstrate that there is evidence of impoverishment of the small Carnivore community in the Rivers State agro‐forestry systems from comparisons between their study area and more heavily forested areas in the central Niger Delta and in Benin. They show that in their study area, only four species were found compared with 5–7 taxa in the central Niger Delta and Benin. Notably, in the three studied markets, the smallest species (i.e., Cṛossarchus platycephalus) accounted for more than 95% of all individuals observed. This species is also the best adapted to forest‐derived grasslands as it feeds essentially on Rodents, which become an abundant food resource in such altered habitats. Thus, Onuegbu et al.'s data suggest a process of functional similarity of biotas over time, associated with the establishment of species that have similar 'roles' in the ecosystem and with the loss of those possessing unique functional 'roles'.

Comparison of our results with data obtained for the same area about a decade ago shows that although only three species were recorded then, their relative abundances were more equilibrated than in the present study. There were also significant differences in the frequency of occurrence of the various species, particularly the dramatic increase in the relative abundance of Cṛossarchus platycephalus; in 2009, the species was not observed. This is a clear signal of an ongoing species substitution process, which mirrors data on Cobras from the same area, where Naja nigricollis (a mainly savannah species) was clearly substituting Naja melanoleuca (a mainly forest species) in almost every suitable habitat in the region. Analogous to the patterns observed for Cobras, Cṛossarchus platycephalus, a small group‐living species typical in deforested and heavily altered landscapes, is taking over This species is nowadays very common in the deforested grasslands and plantations of the Port Harcourt region, possibly due to the greater abundance of rodents (their main food type) in these habitats.

Onuegbu et al.'s study also confirmed the occurrence of Nandinia binotata in the surroundings of Port Harcourt, though this species was not considered present in the Niger Delta in 2007. This species is also one of the most intensively traded Carnivore species in African forests.

In Onuegbu et al.'s study, they show there is clear seasonal pattern in the number of carcasses of Cṛossarchus platycephalus that peaked during the rainy months. Although for the other three species the sample was too small for any statistical analysis, in the Niger Delta, Nandinia binotata was previously recorded slightly more often during the wet season with no significant inter‐seasonal difference. In Gabon, Nandinia binotata females gave birth to young from June to January each year (that is in both dry and wet seasons), which is apparently linked to fruiting seasonality as this species is mainly frugivorous.

Finally, in two of the species recorded (Cṛossarchus platycephalus and Civettictis civetta) the sex ratio of the traded individuals was significantly female‐skewed. Data on sex ratios of African small carnivores are very scanty, and thus, comparisons are problematic. Female‐skewed sex ratio was also observed in Nandinia binotata in Gabon. but sex ratio was even in Nigerian Nandinia binotata and Civettictis civetta, or males were significantly more numerous than females in other small Carnivore species of bushmeat markets in Nigeria, including Genetta sp..

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Aonyx capensis: Genetic diversity of African Clawless Otters in urbanised areas of Gauteng, South Africa.

Recent decades have seen a rapid increase in urbanised areas around the world, with profound impacts on the wildlife of the areas into which cities are expanding. Many cities do contain areas of parkland or other open spaces that can be utilised by wildlife, but animals vary in their ability to utilise such spaces, with species that require large territories generally faring particularly badly. Gauteng Province of South Africa has a complex landscape comprising urban areas surrounded by less transformed periurban areas. This is home to two species of Otters, African Clawless Otter, Aonyx capensis, and the Spotted-necked Otter, Hydrictis maculicollis, both of which are classified as Near Threatened under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species, though to date their have been no studies of the populations of either of these.

A four year old, male African clawless otter, on the bank of the Kavango river, Namibia. Mark Paxton/Shamvura Camp/Wikimedia Commons.

In a paper published in the South African Journal of Science on 30 July 2019, Damian Ponsonby of the School of Animal, Plant and Environmental Sciences at the University of the Witwatersrand, Thabang Madisha of the National Zoological Gardens of South Africa, Ute Schwaibold, also of the
School of Animal, Plant and Environmental Sciences at the University of the Witwatersrand, and Desiré Dalton, also of the National Zoological Gardens of South Africa, and of the Department of Zoology at the University of Venda, describe the results of a study of the population of Otters in Gauteng using DNA extracted from spraint (feces), a procedure previously used successfully on European Otter populations.

Ponsonby et al. collected samples of Otter spraint from sites at 5 km intervals along eight rivers across the Crocodile and Vaal river catchments, obtaining a total of 211 samples. Of these 171 were identified by genetic markers as belonging to the African Clawless Otter, while eight came from the
Spotted-necked Otter and 32 could not be identified. Due to the small sample size the Spotted-necked Otter was excluded from the rest of the study.

Of the 171 African Clawless Otter spraint samples, two were found to have come from the same animal, giving a total of 170 individual Otters in the study. However, these Otters showed very little genetic diversity, suggesting that they have undergone one or more local extinction events, with the area being recolonised by the decedents of a small number of individuals. As well as hinting at past problems for the population, the low genetic diversity observed also makes the population more vulnerable to future threats, particularly diseases, which can spread rapidly through populations with low genetic diversity.

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