**5. Conclusions**

We have presented a taxonomic inventory of squamate reptiles for a well-sampled lowland rainforest site in southern Peru. Our results provide further support for the existence of a western Amazonian richness gradient, whereby species richness for some groups of plants and animals declines as one moves from the northwestern Amazon basin (Rio Amazonas, Peru; Ecuadorian Amazon) to the southwest (southern Peru). Further studies of this gradient (Table 2) can provide insights into the evolutionary and ecological processes that have shaped Amazonian biodiversity more generally. However, numerous challenges remain, especially for groups such as squamate reptiles, which are difficult and costly to sample. For example, de Fraga et al. [17] estimate the cost of finding a single snake in the Amazon to be approximately \$120, a number that accords well with our own field costs. Martins and Oliveira [55], in one of the most comprehensive ecological studies of Amazonian snakes, estimated that approximately 3.25 h of survey effort were required per individual snake capture. To obtain a reasonably comprehensive taxonomic inventory of reptiles at any single site in the

Amazon is a daunting task, requiring many thousands of person-days of field time. Consequently, our understanding of the ecology of tropical reptile communities lags far behind that of many other taxa. Despite numerous human impacts on Amazonian forest communities, it is not ye<sup>t</sup> possible to develop conservation and managemen<sup>t</sup> strategies for most squamate reptile taxa, owing to the lack of basic information on the distribution and abundance of species.

**Author Contributions:** Conceptualization, D.L.R. and R.v.M.; methodology, D.L.R., R.v.M., M.C.G. and A.R.D.R.; formal analysis, D.L.R. and A.R.D.R.; investigation, D.L.R., R.v.M., M.C.G. and A.R.D.R.; resources, D.L.R., M.C.G., A.R.D.R. and R.v.M.; data curation, M.C.G., R.v.M. and D.L.R.; writing—original draft preparation, D.L.R.; writing—review and editing, D.L.R., R.v.M., A.R.D.R., M.C.G.; visualization, A.R.D.R. and D.L.R.; project administration, D.L.R. and R.v.M.; funding acquisition, D.L.R., A.R.D.R. and R.v.M.

**Funding:** This research was supported by a fellowship from the David and Lucile Packard Foundation to D.L.R., and by the University of Michigan Museum of Zoology. RvM thanks the Amazon Conservation Association, Conservación Amazónica-ACCA, Wildlife Conservation Society, National Science Foundation, and National Geographic Society.

**Acknowledgments:** For field assistance, we thank E.S. Vargas Laura, C. Macahuache Díaz, R. Villarcorta Díaz, E. Durand Salazar, E.M. Iglesias Antonio, N. Tafur Olortegui, O.L. Huacarpuma Aguilar, Y. Casanca Leon, R. Santa Cruz, C. Sanchez Paredes, H. Cárdenas, V. Herrera, A. Guzmán, C. Alarcón, J.C. Cusi, P. Cerda, M. A. Cowan, D. Nondorf, M. R. Grundler, I. A. Holmes, J. G. Larson, G. Pandelis, I. Russell, B. Sealey, P. O. Title, E. P. Westeen, M. Medina-Müller, N. Carrillo, R. Jennings, K. E. Reider, R. McCracken, Z. Lange, P. Campbell, M. Semeniuk, A. Smith, J. Vollmar, M. Vollmar, C. Pinnell, J. M. Jacobs, S. Kiriakopolos, M. Roscheisen, J. Valdivia, J. Huamán, L. Flores, V. Quispe, J. Martinez, R. Thupa, H. Collado, J. Perez, and park rangers of the Los Amigos Conservation Concession. We especially acknowledge A. Basto, C. Castañeda, J. Valdez, C. Quispe, other members of the supporting sta ff at LABS, and support from the Amazon Conservation Association. We thank G. Schneider, C. Aguilar, J. Cordova Santa Gadea, J. C. Cusi, M. Fernandez, and C. Whitcher for assistance with specimen logistics at UMMZ and MUSM, and R. Murrell for assistance with financial logistics at the UMMZ. M. Finer generously shared reptile species lists for Yasuní and Tiputini. G. Gagliardi, N. Hidalgo, and T. Paine shared several new squamate records for Los Amigos with us. H. Braz, T. Guedes, N. R. de Albuquerque, and P. Melo Sampaio generously shared information about several snake records from Brazil. Research and collecting permits were issued by the Instituto Nacional de Recursos Naturales (INRENA), the Dirección General Forestal y de Fauna Silvestre (DGFFS), and the Servicio Nacional Forestal y de Fauna Silvestre (SERFOR), Peru (R.D. 11-2008-INRENA-IFFS- DCB, 120-2012-AG-DGFFS-DGEFFS, 064-2013-AG- DGFFS-DGEFFS, 292-2014-AG-DGFFS-DGEFFS, R.D.G. 029-2016-SERFOR-DGGSPFFS, R.D.G. 405-2016-SERFOR-DGGSPFFS).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
