A review of taxonomic history and phylogeography for the spider monkeys (genus Ateles), with habitat suitability modelling for Amazonian Ateles

Grant, Chloe

Abstract

The spider monkeys (genus Ateles) (É. Geoffroy Saint-Hilaire, 1806) are one of the most
widespread platyrrhine primates, ranging from the tropical and subtropical rainforests of the
Yucatan peninsula and coastal regions of Vera Cruz state in Mexico, through central America,
from the Pacific coast of Ecuador to Guyana and Suriname in the north-eastern region of South
America, all the way to northern Bolivia. They are primates that belong to the family Atelidae
(Gray, 1825), and sub-family Atelinae (Gray, 1825), the prehensile tailed monkeys. The genus
encompasses broad species richness with 16 currently recognised Ateles species and subspecies
(PSG, 2022), and are considered key indicator species in the forest who have a large impact on
ecosystem health and stability. They are severely threatened by deforestation, habitat
degradation, and climate change as they have restricted habitat preferences facilitated by their
specialist frugivorous diet and fission-fusion social system. Although multiple authors have
debated and revised Ateles' taxonomy, evolutionary relationships, and biogeography, the main
outcome has been confusion, which impedes the ability to implement conservation actions. This
dissertation provides a comprehensive review of information and studies concerned with the
taxonomic and biogeographic history, as well as the distribution and conservation status of the
spider monkeys. It does this in an attempt to exemplify the decades of research the genus has
been subjected to, and act as an inclusive source of knowledge for academics and students
interested in such topics. Additionally, it explores the genetic relationships of the Ateles where
mitochondrial DNA (mtDNA) sequences were available using the maximum likelihood (ML)
method of phylogenetic inference. We created two phylogenetic trees using (1) whole mtDNA
sequences and (2) sequences from the cyt-B gene region of mtDNA. A map was created of both
trees to show the geographic information attached to the sequences to try and observe if
location was a factor in the phylogenetic delineation and topology of the tree. It was found that
mtDNA sequences construct a clearer and more well supported tree by using the bootstrap (BS)
nonparametric method of reliability. Monophyletic clades were identified in both trees, as well as
a visible distinction of two separate A. chamek clades, of which the geographical information
attached supports the recognition of a new taxa possibly due to a speciation event that
reproductively isolated the two clades. Withal, the cyt-B tree only represents 12 out of the 16
currently recognised Ateles species and subspecies (PSG, 2022) and the mtDNA tree only
includes sequences from five species, no subspecies are represented in this tree. This fact may
impede the results of the phylogeny. I recommend a full taxonomic revision of the genus with
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each species accounted for and geographically labelled. Finally, this dissertation uses species
distribution modelling to assess habitat suitability for Amazonian species of Ateles, while trying
to uncover the true area of occupancy (AOO) within the predicted IUCN extent of occurrence
(EOO). A Pearson's correlation was evaluated between variables used to measure habitat
suitability in accordance with the distribution data to determine which environmental variables
were the most important in the different regions inhabited by the separate species. The
maximum entropy algorithm (MAXENT) (version 3.4.3) with "dismo" (version 1.3-5) in the
statistical computer program RStudio (version 4.1.1) (RStudio Team, 2022) was used to create
the models. I discovered that the AOO is substantially smaller for each Amazonian Ateles
species than that suggested by the IUCN, and habitat suitability is often poor (<0.5) in these
regions. High habitat suitability zones (>0.7) are scattered across the landscape and are not
always governed by protected areas. The results show that precipitation and temperature
related variables had the greatest influence on the outcomes of the MAXENT models. The
priorities for conservation of the Amazonian Ateles lies in the successful development and
expansion of protected areas (PAs), specifically in the regions occupied by A. marginatus and A.
hybridus where the majority of suitable habitat falls outside of the jurisdiction of PAs, and hence
these forests will be the first to be fragmented and depleted. I recommend that the
conservation status of the Ateles be re-assessed by the IUCN based on these models, and
propose that assessments of all spider monkey species be carried out more frequently due to
the rapid transformation and degradation of the tropical rainforests of Central and South
America.

• Thesis Type: Thesis
• Deposit Date: Oct 6, 2023
• Publicly Available Date: Oct 30, 2023
• Award Date: Sep 29, 2023