Abstract
Understanding the ecology and evolutionary history of symbionts and their hosts requires accurate taxonomic knowledge, including clear species boundaries and phylogenies. Tortoise mites (Mesostigmata: Uropodoidea) are among the most diverse arthropod associates of bark beetles (Curculionidae: Scolytinae), but their taxonomy and host associations are largely unstudied. We tested the hypotheses that (1) morphologically defined species are supported by molecular data, and that (2) bark beetle uropodoids with a broad host range comprise cryptic species. To do so, we assessed the species boundaries of uropodoid mites collected from 51 host species, across 11 countries and 103 sites, using morphometric data as well as partial cytochrome oxidase I (COI) and nuclear large subunit ribosomal DNA (28S). Overall, morphologically defined species were confirmed by molecular datasets, with a few exceptions. Twenty-nine of the 36 uropodoid species (Trichouropoda, Nenteria and Uroobovella) collected in this study had narrow host ranges, while seven species had putative broad host ranges. In all but one species, U. orri, our data supported the existence of these host generalists, which contrasts with the typical finding that widespread generalists are actually complexes of cryptic specialists.
Highlights
Increased access to nucleotide sequencing over the last twenty years has led to exponential growth of molecular-based taxonomy [1]
Most (76%) of the host associations observed in this study represent new records, and 19 of the 23 described species collected in this study had new host records (Table 3)
All cytochrome oxidase I (COI) analyses suggested that each trematurid (Trichouropoda and Nenteria) species was monophyletic, with the exception of T. moseri and T. polytricha
Summary
Increased access to nucleotide sequencing over the last twenty years has led to exponential growth of molecular-based taxonomy [1]. Species boundaries of symbionts are frequently assessed using molecular markers, and it is often revealed that an apparent widespread host generalist is not a generalist, but rather a complex of cryptic species with narrower host ranges. Morphological and molecular analyses of Uroobovella nova (Urodinychidae), a single widespread putative generalist uropodoid species collected from silphid beetles worldwide, is a complex of cryptic species with varying degrees of host specificity [7]. 97 species of mites representing 65 genera and 40 families have been collected from under the bark of scolytine infested pine trees [9]. Many or most of these mites reside, feed and reproduce in the galleries of bark beetles, and they attach to dispersing scolytines, hitching a ride to new host trees or coarse woody debris, which would otherwise be difficult to access for most free-living mites
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