Inland aquatic organisms almost ubiquitously display a pattern of marked provincialism characterized by substantial population differentiation and genealogical discontinuities. This is the result of strong priority effects and local adaptation following dispersal and colonization of new habitats. We present a case that defies this biogeographic paradigm. We have investigated the phylogeography of the fairy shrimp Streptocephalus torvicornis across its circum-Mediterranean and Eurasian distribution. Based on three independent datasets, namely sequence variation at 12S and 16S rRNA, cyst morphology and male second antenna characters, we discern a pattern of extensive genetic and morphological homogeneity pointing to unhindered gene flow and widespread connectivity among populations. These intriguing findings may provisionally be explained by (i) a high dispersal frequency overwhelming the ability of a population to maintain resource monopolization, (ii) an outbreeding vigour opportunity offered to secondary immigrants, (iii) an ecological equivalence of genotypes generating long-term immigration-extinction equilibria and buffering genetic diversity over spatial scales, (iv) enhanced bird-mediated dispersal in
When symbioses between insects and bacteria are discussed, the origin of a given association is regularly of interest. We examined the evolution of the symbiosis between reed beetles (Coleoptera, Chrysomelidae, Donaciinae) and intracellular symbionts belonging to the Enterobacteriaceae. We analyzed the partial sequence of the 16S rRNA to assess the phylogenetic relationships with bacteria we found in other beetle groups (Cerambycidae, Anobiidae, other Chrysomelidae). We discuss the ecology of each association in the context of the phylogenetic analysis. The bacteria in Sagra femorata (Chrysomelidae, Sagrinae) are very closely related to those in the Donaciinae and are located in similar mycetomes. The Sagrinae build a cocoon for pupation like the Donaciinae, in which the bacteria produce the material required for the cocoon. These aspects support the close relationship between Sagrinae and Donaciinae derived in earlier studies and make a common ancestry of the symbioses likely. Using PCR primers specific for fungi, we found Candida sp. in the mycetomes of a cerambycid beetle along with the bacteria.
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