Thesis Defence: Reconstructing the mating system of Santa Cruz Galapagos giant tortoises with implications for the conservation of a critically endangered species

Carolyn Jessop, supervised by Dr. Michael Russello, will defend their thesis titled “Reconstructing the mating system of Santa Cruz Galapagos giant tortoises with implications for the conservation of a critically endangered species” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Carolyn Jessop’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.

Abstract

Mating systems influence the behavioural and eco-evolutionary processes of a species, so understanding a species mating system can inform conservation strategies. The two species of Galapagos giant tortoise on Santa Cruz Island (Chelonoidis donfaustoi and C. porteri) are keystone species in their respective habitats. To assist in conservation efforts, more knowledge of their mating systems in wild populations is necessary, including if multiple paternity is present. To enable investigation of reproductive behaviour in Santa Cruz giant tortoises, we developed a genotyping in thousands by sequencing (GT-seq) panel that can identify species and individuals and estimate relatedness. Given the conservation status of these species, we designed and optimized the panel to genotype minimally invasive cloacal swab samples. The developed panel includes 325 SNPs; 38 targeted for species identification and 287 for individual identification and relatedness estimation. Genotypic data collected from 220 samples from 42 nests and attending mothers were be used to reconstruct the mating system to support nesting data and to determine the presence of multiple paternity within the population. In total, five of the 14 females sampled had nests with different fathers in the same nesting season. Four of these females had nests where two fathers contributed, showing evidence for multiple paternity. Overall, the findings of this research contribute to existing literature on Galapagos tortoise mating systems, which can help inform future management decisions within the system.