Systematics of harvester ants (Messor) in Israel based on integrated morphological, genetic, and ecological data

Abstract

Harvester ants of the genus Messor are considered ecosystem engineers, whose distribution is broadly influenced by a variety of environmental factors. Although distinct Messor species have been reported to inhabit different habitats, their taxonomy in Israel remains largely ambiguous, hampering the proper ecological characterization of these species. Here, we applied an integrative species delimitation approach combining morphology-based identification, phylogenetic analyses of nuclear and mitochondrial genes, and ecological niche modelling to investigate the phylogenetic relationships among Messor species in the small but ecologically diverse region of Israel. Our analyses of mitochondrial genes revealed the presence of at least 13 well-defined lineages, whereas only seven were supported by the analysis of the nuclear genes. However, the concatenated tree that included all the three markers supported 11 lineages. Among two of the lineages-in M. semirufus and in a group of ants closest in resemblance to M. grandinidus- we identified 3-4 clades that were well established on most trees, inviting further study. In addition, we reveal three undescribed species and raise two subspecies to species rank, highlighting the high diversity of harvester ants in Israel. Ecological niche modelling consistently supported the observed distribution of species, with soil type and average annual temperature being the most influential factors. These results demonstrate that species distribution modelling can serve as a valuable component of integrative species delimitation. We call for future studies to investigate these fascinating lineages of one of the most prominent and ecologically important genera of ants in the Mediterranean Basin.