Evolution of host- and habitat association in the wood-feeding cockroach, Cryptocercus

Abstract

Members of the cockroach genus Cryptocercus are subsocial insects that live in temperate forests and feed on decomposing logs. At present, seven species are recognized worldwide: four in the eastern USA, one in the western USA, and one each in Russia and China. Genetic variation within and among the Nearctic species has been characterized extensively in previous studies. However, whether there has been a corresponding divergence in the host and habitat association of Cryptocercus species is not known. Here, we report on differences in host and habitat association among six of the seven Cryptocercus species, estimated from field observations, elevation data, and land cover data. Our results indicated that the eastern and western USA species differ from one another in their distribution patterns, abundance, and habitat association. The eastern USA species are associated largely with deciduous forests, whereas the western USA and the Russian species are associated with evergreen forests. Thus, the eastern USA species, which are evolutionarily the most recent ones, have adapted to a different set of tree species relative to the basal species. There were also differences in the habitat association of the various species. Specifically, in the eastern USA, Cryptocercus darwini, evolutionarily the most recent species, occupied a habitat that is predominantly at low elevation [<400 m above sea level (ASL)] while all the other Nearctic species and the Russian species occupied a habitat that is at relatively higher elevations (>400 m ASL). Mapping of the above traits on a phylogenetic tree revealed that the evolutionary trend in Cryptocercus with regard to host and habitat association has been toward the utilization of low elevation habitats dominated by deciduous forests. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 163–172.

Evolution in the genus Cryptocercus (Dictyoptera: Cryptocercidae): no evidence of differential adaptation to hosts or elevation

“…By definition, a host is ‘any organism that provides food or shelter for another organism’ (Lincoln, Boxshall & Clark, 1998); my discussion therefore centres on whether or not a given plant taxon is known to serve as host to the cockroach. This contrasts with the more ambiguous ‘host associations’ and ‘large scale features of the habitat’ to which Kambhampati et al . (2002) refer.…”

“…The ‘large scale characterization of the habitat’ by Kambhampati et al . (2002) succeeds only in giving a general description of already well‐characterized regions.…”

“…The wingless, wood‐feeding cockroach genus Cryptocercus lives in and feeds on moist, rotting logs in montane, forested habitats of the northern hemisphere. Although Kambhampati, Clark & Brock (2002) (abstract, p.163) indicate that ‘there are 7 species recognized world‐wide’, the current taxonomy of the genus is much more convoluted. The genus is found in two regions of the Palearctic, and two regions of the Nearctic.…”

“…The null hypothesis regarding host association in Cryptocercus is that all taxa in the genus are generalists; they depend on the presence of moist, rotted logs, with the host range determined by the species composition of the inhabited forest (Nalepa & Bandi, 1999). Kambhampati et al . (2002) rejected this hypothesis, asserting that there has been an evolutionary shift from evergreen to deciduous host use within the genus.…”

“…The goal of this paper is to re‐examine existing literature on host use and elevational affinities in the genus Cryptocercus , to determine if the hypothesis of Kambhampati et al . (2002) of differential adaptation to these two features of the environment is robust.…”