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Multiple origins of elytral reticulation modifications in the west palearctic Agabus bipustulatus complex (coleoptera, dytiscidae).

ABSTRACT: The Agabus bipustulatus complex includes one of Europe's most widely distributed and common diving beetles. This complex, which is known for its large morphological variation, has a complex demographic and altitudinal variation in elytral reticulation. The various depth of the reticulation imprint, both in smaller and larger meshes, results in both mat and shiny individuals, as well as intermediate forms. The West Palearctic lowland is inhabited by a sexually dimorphic form, with shiny males and mat females. In mountain regions, shiny individuals of both sexes are found intermixed with mat individuals or in pure populations in central and southern areas, whereas pure populations of mat individuals are exclusively found in the northern region at high altitude. Sexual selection is proposed as a driving force in shaping this variation. However, the occurrence of different types of reticulation in both sexes and disjunct geographical distribution patterns suggest an additional function of the reticulation. Here we investigate the phylogeographical history, genetic structure and reticulation variation of several named forms within the Agabus bipustulatus complex including A. nevadensis. The molecular analyses recognised several well-supported clades within the complex. Several of the named forms had two or more independent origins. Few south European populations were uniform in reticulation patterns, and the males were found to display large variation. Reticulation diversity and population genetic variability were clearly correlated to altitude, but no genetic differences were detected among populations with mixed or homogenous forms. Observed reduction in secondary reticulation in female and increased variance in male at high altitude in South Europe may be explained by the occurrence of an additional selective force, beside sexual selection. The combined effect of these selective processes is here demonstrated in an extreme case to generate isolation barriers between populations at high altitudes. Here we discuss this selective force in relation to thermal selection.

SUBMITTER: Drotz MK

PROVIDER: S-EPMC2815794 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Multiple origins of elytral reticulation modifications in the west palearctic Agabus bipustulatus complex (coleoptera, dytiscidae).

Drotz Marcus K MK Brodin Tomas T Nilsson Anders N AN

PloS one 20100203 2

The Agabus bipustulatus complex includes one of Europe's most widely distributed and common diving beetles. This complex, which is known for its large morphological variation, has a complex demographic and altitudinal variation in elytral reticulation. The various depth of the reticulation imprint, both in smaller and larger meshes, results in both mat and shiny individuals, as well as intermediate forms. The West Palearctic lowland is inhabited by a sexually dimorphic form, with shiny males and ...[more]

PMID: 20140264

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Project description:The Holarctic diving beetle genus Graphoderus (Dytiscinae, Aciliini) contains relatively few and well-known species but these may still be difficult to identify based on external characters. A taxonomic problem in the eastern Palearctic was discovered that relates to the Palearctic Graphoderus zonatus (Hoppe, 1795) and the Nearctic Graphoderus perplexus Sharp, 1882. Based on qualitative and quantitative characters, especially on male genitalia which have been poorly studied in the past, it is shown that eastern Palearctic specimens identified by previous authors as either of the two species in fact belongs to a third species. The synonymized name Graphoderus elatus Sharp, 1882, is reinstated as a valid species (stat. n.) and a lectotype is designated from the mixed syntype series. The male genitalia of all known Graphoderus species have been examined and an illustrated identification key to the genus is provided. The three species in the complex of focus, Graphoderus elatus, Graphoderus zonatus and Graphoderus perplexus are found to have allopatric distributions; Graphoderus perplexus in the Nearctic region, Graphoderus zonatus in the west Palearctic region and eastwards to the Yenisei-Angara river and Graphoderus elatus east of the Yenisei-Angara river. All previous records of either Graphoderus zonatus or Graphoderus perplexus in the east Palearctic, east of the Yenisei-Angara river turned out to be misidentified Graphoderus elatus. This conclusion also brings with it that dimorphic females, thought only to be present in the single subspecies Graphoderus zonatus verrucifer (CR Sahlberg, 1824), proved to be present also in a second species, Graphoderus elatus. The dimorphic female forms is either with dorsally smooth elytra and pronotum or conspicuously granulated elytra and wrinkly pronotum. As has been shown in Graphoderus zonatus verrucifer there is a correlation between the occurrence of granulate female forms in a population and an increase in the number of adhesive discs on pro- and mesotarsus in males within Graphoderus elatus.

Project description:BACKGROUND: Problems associated with resistant mosquitoes and the effects on non-target species by chemicals, evoke a reason to find alternative methods to control mosquitoes, like the use of natural predators. In this regard, aquatic coleopterans have been explored less compared to other insect predators. In the present study, an evaluation of the role of the larvae of Acilius sulcatus Linnaeus 1758 (Coleoptera: Dytiscidae) as predator of mosquito immatures was made in the laboratory. Its efficacy under field condition was also determined to emphasize its potential as bio-control agent of mosquitoes. METHODS: In the laboratory, the predation potential of the larvae of A. sulcatus was assessed using the larvae of Culex quinquefasciatus Say 1823 (Diptera: Culicidae) as prey at varying predator and prey densities and available space. Under field conditions, the effectiveness of the larvae of A. sulcatus was evaluated through augmentative release in ten cemented tanks hosting immatures of different mosquito species at varying density. The dip density changes in the mosquito immatures were used as indicator for the effectiveness of A. sulcatus larvae. RESULTS: A single larva of A. sulcatus consumed on an average 34 IV instar larvae of Cx. quinquefasciatus in a 24 h period. It was observed that feeding rate of A. sulcatus did not differ between the light-on (6 a.m. - 6 p.m.), and dark (6 p.m. - 6 a.m.) phases, but decreased with the volume of water i.e., space availability. The prey consumption of the larvae of A. sulcatus differed significantly (P < 0.05) with different prey, predator and volume combinations, revealed through univariate ANOVA. The field study revealed a significant decrease (p < 0.05) in larval density of different species of mosquitoes after 30 days from the introduction of A. sulcatus larvae, while with the withdrawal, a significant increase (p < 0.05) in larval density was noted indicating the efficacy of A. sulcatus in regulating mosquito immatures. In the control tanks, mean larval density did not differ (p > 0.05) throughout the study period. CONCLUSION: the larvae of the dytiscid beetle A. sulcatus proved to be an efficient predator of mosquito immatures and may be useful in biocontrol of medically important mosquitoes.

Dataset Information

Multiple origins of elytral reticulation modifications in the west palearctic Agabus bipustulatus complex (coleoptera, dytiscidae).

Publications

Multiple origins of elytral reticulation modifications in the west palearctic Agabus bipustulatus complex (coleoptera, dytiscidae).

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