Genetic structure and demographic history of the dung beetle Deltochilum guildingii (Scarabaeinae): implications for conservation of the Tropical Dry Forest in the Colombian caribbean

In the Colombian Caribbean, the Tropical Dry Forest (TDF) is among the most important ecosystems for conservation providing both economic and regulatory services to local communities and it is the habitat of many dung beetles. Particularly, the species Deltochilum guildingii is notable for its large size and greater capacity to bury organic matter, thus facilitating the recycling of soil nutrients and seed germination. The current degradation of the TDF, however, may have adverse effects on its population genetics. In this study, based on 2,587 single nucleotide polymorphisms (SNPs) generated by restriction-site associated DNA sequencing in 60 individuals of D. guildingii in six TDF fragments in the Colombian Caribbean (departments of Guajira, Magdalena, Cesar, Atlántico, Bolívar, and Sucre), we aimed to estimate genetic diversity and its relationship with fragmentation. Moreover, we evaluated spatial patterns of genetic structure, and inferred D. guildingii demography history. Our results showed reduced heterozygosity in all populations with the lowest for the Magdalena fragment. There was no relationship between genetic diversity and fragment area, perimeter, or degree of insularization. Multivariate and Bayesian clustering analyses of genetic structure identified two genetic groups of biogeographic affinity: one pertains to the northern departments (Guajira, Magdalena, and Cesar) and the other to the south (Montes de María and Piojó). In addition, a population expansion was estimated 2.5 million years ago during the Pleistocene, which coincided with the time of TDF diversification in Colombia and of the genus Alouatta, the primates that provide the principal source of excrement to D. guildingii.