Please enable JavaScript.
Coggle requires JavaScript to display documents.
Novel island species elucidate a species complex of Neotropical crocodiles…
Novel island species elucidate a species complex of Neotropical crocodiles
Introduction
Conservation strategies require accurate population-level phylogenetic estimates; critical in Crocodylus because of poorly understood evolutionary history
relationships between the four extant neotropical species have been controversial due to inconsistent relationships, sparse fossil records, and hybridization
This study uses a combination of genomic and phenotypic data to evaluate species and population divergence to reconstruct the history
examined population genomics, morphology, and ecology of two remote populations of Crocodylus acutus
Methods
Tissue samples from eight localities in Mexico were used (71 samples of acutus, 24 of moreletii and 5 of rhombifer)
DNA was extracted by phenol:chloroform:isoamyl alcohol, assessed by electrophoresis and purified; raw illumina reads were analyzed
Nucleotide diversity per population was calculated, two methods (ADMIXTURE V.1.3.0 & DAPC) were used to explore genetic structure of populations
BEAST2 was used to reconstruct the phylogenetic history of the populations.. Diffusion Approximation Demographic Inference was performed based on the allele frequency spectrum
Two dimensional geometric morphometric analyses were conducted using GEOMORPH V.3.0.7 to investigate cranial shape variation across Neotropical crocodile populations
Results
Genomic variation was relatively high in most populations sampled. The Cozumel and Banco Chinchorro Crocodylus populations had the highest number of unique alleles
Inbreeding coefficients in all populations are close to zero indicating heterozygosity within Hardy-Weinberg expectations
Genetic differentiation (FST)
C. moreletii populations range from 0.021 to 0.112, suggesting low genetic differentiation
The Pacific Mexico C. acutus populations are well differentiated from other C. acutus populations (FST = 0.335–0.621)
Panamanian population pairs of C. acutus show a low degree of differentiation (FST = 0.139–0.278)
Insular populations of Cozumel and Banco Chinchorro have the highest FST values when compared to Pacific Central America and Pacific Mexico C. acutus populations (FST = 0.481–0.582) and the lowest when compared to Caribbean Central America C. acutus populations (FST = 0.388–0.450)
molecular phylogeny
C. moreletii divergence separating it from C. acutus and C. rhombifer
C. rhombifer is sister to C. acutus populations
C. acutus populations are separated into three main groups: a group of the insular Yucatan populations, a Panamanian cluster, and a Pacific Mexico cluster.
genetically divergent insular populations also present morphological differences to other Crocodylus species
Discussion
surprisingly high genomic and cranial phenomic variation within this widespread species
high genomic divergence of Pacific Mexican populations from all other sampled C. acutus populations
high diversity present in Cozumel and Banco Chinchorro; have the highest number of alleles, highest nucleotide diversity, and low inbreeding coefficients
insular populations of Banco Chinchorro and Cozumel are morphologically, genetically, and ecologically distinct and reproductively isolated from each other and coastal populations; paper suggestions speciation
Declaring the crocodile population of Banco Chinchorro as a new species would empower decision makers and conservation actors to obtain funding for the surveillance and conservation of this protected area and its biodiversity