Genetic and morphometric variation of two focal snapper species (Lutjanus bohar and Lutjanus gibbus) in the Chagos Archipelago

Genetic and morphological variation were investigated for two snapper species: two-spotted snapper (Lutjanus bohar) and humpback red snapper (Lutjanus gibbus), at four atolls (Diego Garcia, Egmont, Peros Banhos and Salomon) within the Chagos Archipelago in the Indian Ocean. This is an area which has some of the most undisturbed and remote corals on earth, and is therefore an ideal location for understanding how species within reef communities might adapt to environmental change and degradation. Three separate approaches were used to carry out this investigation: 43 individual L. bohar were screened for genetic variation at the cytochrome c oxidase subunit 1 (CO1) mitochondrial DNA (mtDNA) gene. Results show overall high mtDNA diversity for the populations, but low nucleotide divergence between haplotypes. The species constitutes a well-mixed population with a ubiquitous, predominant haplotype, shared by 51% of specimens. 129 L. bohar and 101 L. gibbus individuals were assessed for morphometric (size and shape) variability. A significant difference in mean size for both lutjanid species was detected between Diego Garcia and each of the three other atolls. For both species, smallest individuals were found at Diego Garcia, where recreational fishing has depleted fish biomass in general and may have also directly impacted the abundance of large lutjanids. Variations in shape (weight, circumference and body depth, relative to fork length) between locations were not statistically significant when collinearity was accounted for. 118 L. bohar and 69 L. gibbus were selected for population structure analysis using a next-generation sequencing RAD-seq approach. A genomic analysis of population structure was carried out using genome wide SNP markers. Weak population structure was detected between all atolls, for both species (Fst 0.001-0.009) indicating good genetic connectivity among lutjanids throughout the Chagos Archipelago. The combined findings of this research are consistent with the hypothesis that there is little population structure for L. bohar and L. gibbus within the Chagos Archipelago and that populations are well connected. As a result, both species are likely to be genetically homogenous throughout the geographic region. The fact that morphometric variation between atolls was restricted to differences in size indicates a plastic response to food availability rather than an evolutionary adaptive response. This research represents the first comparison of genetic and morphometric variation amongst two focal snapper species in the Chagos Archipelago.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2021

Author dc:creator

• Bailey, Abigail

Contributors dc:contributor

• Thompson, Stewart
• Taylor, Michelle

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/61tf-1e19

OAI identifier oai:identifier

tle:505d657c-db6d-40df-bca8-f732637beffc:d6bd9758-527a-46cd-bfe2-c433766e8fca:1