ABSTRACT
Molecular genetic analyses of Caribbean populations of the supposedly widespread intertidal oribatid mite Alismobates inexpectatus revealed the existence of a cryptic species. The new species, Alismobates piratus sp. n., shows considerable COI and 18S rRNA gene sequence divergences and although morphometric analyses indicate considerable variation between the taxa, no distinguishing morphological feature could be detected. The extreme intertidal environment is suggested to be responsible for the observed morphological stasis of the two species and vicariance is supposed to be responsible for their speciation. Alismobates piratus sp. n. was found on Hispaniola, Guadeloupe, Barbados and Curaçao indicating a predominant distribution on the Greater and Lesser Antilles, whereas the occurrence of A. inexpectatus is primarily restricted to Central America, the northern Caribbean and the Greater Antilles. Haplotype network analyses indicate distinct geographic structuring and the absence of recent gene flow among the Antillean A. piratus sp. n. populations. Central American and Antillean populations of A. inexpectatus show similar patterns but populations from Bermuda and the Bahamas are characterized by a common origin and subsequent expansion. Genetic landscape analysis demonstrates that vast stretches of open ocean, like the Caribbean Basin and the Western Atlantic, act as rather effective barriers, whereas the continuous continental coastline of Central and North America may facilitate dispersal. Genetic data also indicates that the Gulf Stream plays an important role for the biogeography of intertidal oribatid mites as it may be responsible for the strong link between Central and North American populations as well as for the colonization of Bermuda. Supplementary Information: The online version contains supplementary material available at 10.1007/s13127-023-00624-9.
ABSTRACT
A molecular genetic and morphometric investigation revealed the supposedly widespread Caribbean and Western Atlantic intertidal oribatid mite species Fortuynia atlantica to comprise at least two different species. Although there are no distinct morphological differences separating these taxa, COI and 18S sequence divergence data, as well as different species delimitation analyses, clearly identify the two species. Fortuynia atlantica is distributed in the northern Caribbean and the Western Atlantic and the new Fortuynia antillea sp. nov. is presently endemic to Barbados. Vicariance is supposed to be responsible for their genetic diversification and stabilizing selection caused by the extreme intertidal environment is suggested to be the reason for the found morphological stasis. The genetic structure of Fortuynia atlantica indicates that Bermudian populations are derived from the northern Caribbean and thus support the theory of dispersal by drifting on the Gulf Stream. Haplotype network data suggest that Bermudian and Bahamian populations were largely shaped by colonization, expansion and extinction events caused by dramatic sea level changes during the Pleistocene. A preliminary phylogenetic analysis based on 18S gene sequences indicates that the globally distributed genus Fortuynia may be a monophyletic group, whereas Caribbean and Western Atlantic members are distinctly separated from the Indo-Pacific and Western Pacific species.
