The Mammals of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna, Part 2: Nonvolant Species

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This report describes the results of nonvolant mammal inventory fieldwork at Paracou, a lowland rainforest locality in northern French Guiana, and concludes the faunal analysis introduced by our previous monograph on the bats of Paracou (Simmons and Voss, 1998). Working within a 3–km radius over the course of 202 sampling dates from 1991 to 1994, we recorded a total of 64 nonvolant species by conventional trapping, arboreal platform trapping, pitfall trapping, diurnal and nocturnal hunting, and interviews with local residents. Included in this total species count are 12 marsupials, 9 xenarthrans, 6 primates, 10 carnivores, 5 ungulates, and 22 rodents.

Systematic research with nonvolant mammal specimens collected as voucher material resulted in the discovery of new taxa, documented range extensions of previously described species, and helped resolve many longstanding taxonomic problems: (1) Gracilinanus emiliae (Thomas), herein reported for the first time from French Guiana, is redescribed and its known geographic distribution documented; based on examination of type material and original descriptions, G. longicaudus Hershkovitz is considered a junior synonym of G. emiliae, but Marmosa agricolaiMoojen is not. (2) A new genus is proposed for Gracilinanus kalinowskii Hershkovitz, a taxon previously known only from eastern Peru, in recognition of its trenchant morphological differences from all other known didelphimorph marsupials. (3) Marmosops parvidens (Tate) and M. pinheiroi (Pine), the latter originally described as a subspecies of the former, are distinct species that occur sympatrically at Paracou; based on examination of type material, other taxa hitherto synonymized with M. parvidens are also judged to be valid species, including M. juninensis (Tate) and M. bishopi (Pine). (4) Monodelphis brevicaudata (Erxleben), M. glirina(Wagner), and M. palliolata (Osgood) are all distinct species diagnosable by unique combinations of morphological traits; based on examined specimens, M. brevicaudata (with type locality emended herein as Kartabo, Guyana) appears to be endemic to the Guiana subregion of Amazonia and to include both bicolored and tricolored phenotypes; a neotype from Cayenne, French Guiana, is designated to fix the application of Viverra touan Shaw as the oldest available name for the tricolored form. (5) Saguinus midas (Linnaeus) and S. niger (E. Geoffroy), currently treated as synonyms or conspecific races, are unambiguously diagnosable species that do not appear to be sister taxa; a neotype is designated to conserve current usage ofniger E. Geoffroy for the black-handed tamarin of southeastern Amazonia. (6) Two new small species of Neacomys are described from material collected at Paracou; their diagnostic attributes are documented by detailed comparisons with other like-sized congeners from northern South America. (7) Nectomys melanius Thomas is recognized as a species distinct from N. squamipes(Brants) and N. palmipes J. A. Allen and Chapman; however, N. parvipes Petter is not a valid taxon and is herein synonymized with N. melanius. (8) The diagnostic characters ofNeusticomys oyapocki (Petter and Dubost), a species previously known only from the holotype, are reevaluated and illustrated from freshly collected material. (9) Oecomys auyantepui Tate andO. paricola (Thomas), previously treated as synonyms, are valid species distinguished by consistent cranial differences and occupy allopatric ranges north and south of the Amazon, respectively. (10) A critical examination of small Oecomys specimens from Paracou and other Guianan localities supports the conclusions of other investigators that O. rutilus Anthony and O. bicolor (Tomes) are unambiguously diagnosable species. (11) Oligoryzomys fulvescens(Saussure) and O. microtis (J. A. Allen), currently regarded as valid allopatric species occurring north and south of the Amazon, respectively, are difficult to diagnose unambiguously and may be conspecific; new information is provided about the hitherto ambiguous type locality of the latter taxon. (12) Rhipidomys nitela Thomas is reported from French Guiana for the first time and its previously unpublished diagnostic differences from other congeners are tabulated and discussed. (13) A lectotype is designated for Coendou melanurus (Wagner), and the species is redescribed based on all known specimens in North American and European museums; diagnostic differences between this species and C. insidiosus (Olfers) are illustrated for the first time. (14) A red-rumped agouti (Dasyprocta) is designated as the neotype of Mus agutiLinnaeus to preserve current usage of Dasyprocta prymnolopha (Wagler) for the black-rumped agouti. (15) The diagnostic differences between red and green acouchies (Myoprocta) are discussed and a neotype is designated for Cavia acouchy Erxleben to fix the application of that name to the red species; other nominal taxa of Myoprocta are identified as red or green acouchies based on examination of type material and original descriptions. (16) The diagnostic morphological traits of Proechimys cuvieri Petter and P. guyannensis (E. Geoffroy) are reevaluated and discussed based on character variation in topotypical (French Guianan) material.

Analyses of our sampling results indicate that distinct sets of nonvolant species are effectively sampled by different inventory methods, and that increased sampling effort with any method generally results in more species. Although the rate of discovery of new species always decreases with increasing sample size, none of our graphs of species accumulation indicate that an asymptotic value was reached with any method. Instead, nonparametric statistical extrapolations suggest that the Paracou nonvolant mammal fauna consists of somewhere between 69 and 74 species; by implication, our nonvolant inventory is about 86–93% complete. Most missing species are probably marsupials and rodents, but one or two expected primate species might have been locally extirpated by hunters prior to our fieldwork.

In terms of higher taxonomic composition, the Paracou nonvolant mammal fauna is typical of those found throughout the humid Neotropical lowlands. However, a quantitative analysis of nonvolant faunal similarity at the species level among 12 exemplar rainforest inventories first clusters the Paracou list with others from the Guiana subregion of Amazonia, next with lists from elsewhere in Amazonia, and lastly with Central American lists. Pairwise similarity values likewise show an obvious positive correlation between faunal resemblance and geographic proximity within the Neotropical rainforest biome. At least 24 species (38%) of the Paracou nonvolant fauna are Amazonian endemics, but 18 (28%) are essentially pan-Neotropical in distribution; the remaining 22 species exhibit a variety of distributional patterns that suggest past connections among different sets of currently disjunct rainforested regions.

Species richness comparisons among nonvolant faunal inventories are complicated by a variety of familiar problems including inconsistent methodology, presence or absence of certain key habitats, and uneven sampling effort. A conservative interpretation of sampling results from La Selva (Costa Rica), Paracou, and Manu (Peru), however, suggests progressive increases in richness of about 23% from Central America to the Guianas, and of about the same amount from the Guianas to western Amazonia; over the entire gradient (Central America to western Amazonia), the net increase in observed richness is at least 50%. Whereas rodents are consistently the most diverse clade in all well-sampled nonvolant faunas, rankings of other orders by relative richness exhibit considerable site-to-site variation, at least some of which appears to reflect real geographic differences in taxonomic diversity rather than sampling artifacts.

Nonvolant rainforest mammals are hard to classify into trophic guilds due to behavioral plasticity and incomplete knowledge of relevant natural history. Preliminary guild comparisons among three exemplar faunas, however, suggest that the Paracou nonvolant community is substantially less diverse in arboreal frugivores and more diverse in terrestrial animalivores than are nonvolant communities at some Central American and western Amazonian sites. Subsistence and recreational hunting has clearly affected local populations of some nonvolant mammals at Paracou; whereas popular game species (e.g., large primates) were seldom sighted, density compensation may explain high local densities of certain other taxa (e.g., Potus flavusand Cuniculus paca). Patterns of differential habitat use between closely related nonvolant species at Paracou were mostly observed within the terrestrial granivore/frugivore guild.

Combining these results with those previously reported for the sympatric bat fauna, we recorded a total of 142 mammalian species at Paracou. By statistical extrapolation from our sampling data, the entire local community perhaps contains 155–168 species; because the known French Guianan rainforest mammal fauna contains at least 167 species for which suitable habitat is present in our study area, such estimates are plausible. By implication, our inventory is perhaps 85–92% complete overall.

A synthesis of biogeographic information analyzed in this monograph and by Simmons and Voss (1998) suggests that faunal turnover with increasing geographic distance is much higher for nonvolant mammals than for bats, a necessary consequence of observed group differences in endemicity: whereas many nonvolant rainforest mammals have geographic ranges bounded by obvious topographic or habitat discontinuities (e.g., large rivers, xeromorphic vegetation), most rainforest bats are geographically widespread. Not surprisingly, most of the taxa that usefully define a Guianan center of mammalian endemism are nonvolant species. The geographic limits of Guianan endemism appear to be remarkably similar for mammals, birds, snakes, lizards, and trees, suggesting a common pattern of biotic differentiation.

Overall, the Paracou mammal fauna conforms broadly with previous generalizations about community-wide patterns of diel activity and substrate use by Neotropical rainforest mammals, but appears to diverge significantly from conventional views about trophic structure. Whereas there are many more species of secondary consumers than primary consumers at Paracou, primary consumers appear to outnumber secondary consumers by an equally large margin at some western Amazonian inventory sites. Sampling artifacts perhaps explain some of the community differences observed in such comparisons, but real geographic variation in trophic structure is also apparent.

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