Current geographical ranges of Malagasy dung beetles are not delimited by large rivers

Abstract

Aim We investigated whether the largest river (Mangoro) on the east coast of Madagascar acts as a barrier to dispersal in dung beetles by comparing species composition and genetic differentiation of the most common species on the two banks of the river. Moreover, by analysing the current geographical ranges of all wet forest dung beetle species, possible long‐term effects of the largest rivers on the distribution of species were assessed. Location Madagascar. Methods Dung beetles were sampled with baited pitfall traps at a downstream and an upstream locality on the two banks of the Mangoro River. The most common species, Nanos binotatus (Canthonini), was sequenced for cytochrome c oxidase subunit I (COI; 804 bp) to characterize within‐population diversity and between‐population genetic differentiation. For the analysis of species geographical range boundaries in relation to the position of the largest rivers on the east coast, a database including all the records for 158 wet forest species was used. The congruence of species range boundaries with the positions of the rivers was tested with a randomization test. Results All common species were found on both sides of the Mangoro River. In Nanos binotatus, haplotype and nucleotide diversities ranged from 0.25 to 0.85 and 0.001 to 0.01, respectively. Population differentiation was high and significant in all comparisons (P < 0.01; average FST = 0.61). The differentiation was not significantly higher across than along the river, as would be expected by the riverine barrier hypothesis. There was no indication that the range boundaries of wet forest dung beetle species would generally coincide with the largest rivers in eastern Madagascar. Main conclusions The results provide little support for the riverine barrier hypothesis as an explanation for the current range boundaries of dung beetles in eastern Madagascar. However, extensive deforestation of the coastal regions in eastern Madagascar may have caused a great shrinkage of the ranges of many forest‐dwelling species. Thus the present‐day distributions may not reflect accurately the patterns of the past geographical ranges of the species.

Origin and Diversification of Dung Beetles in Madagascar

“…Knopp et al [ 31 ] compared dung beetle species composition and genetic differentiation between populations on the two sides of the Mangoro River, the largest river on the east coast, but found little support for the hypothesis of rivers functioning as dispersal barriers and influencing patterns of microendemism in dung beetles [ 31 ]. Another recent study compared levels of genetic differentiation between two nearby (∼40 km) forest localities in northeast Madagascar (Marojejy and Anjanaharibe-Sud) and found contrasting patterns in different species (M. Miinala, unpubl.…”

“…Dung beetles are a great example of Madagascar's biological uniqueness: of the almost 300 species described to date, 285 (96%) are endemic, with several endemic genera and 1 endemic subtribe (Helictopleurina in the tribe Oniticellini) ( Figure A1 ). In recent years, knowledge of Malagasy dung beetles has increased greatly with the publication of taxonomic revisions [ 16 – 25 ], reconstruction of molecular phylogenies [ 24 , 26 – 28 ], as well as phylogeographic [ 29 – 31 ] and ecological studies [ 32 – 35 ]. Here we review and summarize the current knowledge on the ecology and evolutionary biology of dung beetles in Madagascar.…”

Evidence for geographic substructuring of mtDNA variation in the East European Hermit beetle (Osmoderma barnabita)

“…A wealth of molecular methods is now available for detecting the level of intraspecific diversity or divergence amongst sub-populations (Todisco et al 2012, Theissinger et al 2013, Drag et al 2015, with sequences of the mtDNA COI gene (mitochondrial DNA cytochrome c oxidase subunit 1 gene) forming a popular target (Williams et al 2006, Hajibabaei et al 2007, Painter et al 2007, Knopp et al 2011, Čandek and Kuntner 2015. Despite distinct constraints on sequence variation in the COI locus (e.g.…”

“…Factors in the demographic history of sub-populations (e.g. isolation, gene flow and gene drift) may explain present-day ranges, differences in ecology and ultimately resource use (Knopp et al 2011, Miraldo and Hanski 2014, Solano et al 2016, Zauli et al 2016. They may also influence current levels of genetic variation, affecting the evolutionary potential of a given (sub)-population (Avise 2000, Weber et al 2000, Dalén et al 2007, Allendorf et al 2013).…”

The Sepik River (Papua New Guinea) is not a dispersal barrier for lowland rain-forest frogs

“…2011), (2) distribution of geographical ranges of species (mammals: Harcourt & Wood 2012; birds: Hayes & Sewlal 2004; insects: Knopp et al . 2011), and (3) phylogeographical analysis (frogs: Symula et al . 2003; insects: Hall & Harvey 2002).…”