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Sexual dimorphism and allometry in the sphecophilous rove beetle Triacrus dilatus.

Marlowe MH, Murphy CA, Chatzimanolis S - PeerJ (2015)

Bottom Line: Linear regressions were run to examine if there were significant relationships between the different measurements.Our results indicated that males had significantly larger mandibles and ocular distances than females, but the overall body length was not significantly different between the sexes.We found no evidence of major and minor forms in either sex.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Tennessee at Chattanooga , Chattanooga, TN , USA.

ABSTRACT
The rove beetle Triacrus dilatus is found in the Atlantic forest of South America and lives in the refuse piles of the paper wasp Agelaia vicina. Adults of T. dilatus are among the largest rove beetles, frequently measuring over 3 cm, and exhibit remarkable variation in body size. To examine sexual dimorphism and allometric relationships we measured the length of the left mandible, ocular distance and elytra. We were interested in determining if there are quantifiable differences between sexes, if there are major and minor forms within each sex and if males exhibit mandibular allometry. For all variables, a t-test was run to determine if there were significant differences between the sexes. Linear regressions were run to examine if there were significant relationships between the different measurements. A heterogeneity of slopes test was used to determine if there were significant differences between males and females. Our results indicated that males had significantly larger mandibles and ocular distances than females, but the overall body length was not significantly different between the sexes. Unlike most insects, both sexes showed positive linear allometric relationships for mandible length and head size (as measured by the ocular distance). We found no evidence of major and minor forms in either sex.

No MeSH data available.


Related in: MedlinePlus

Scatter plot and linear regression between elytra length and left mandible for males and females.N = 29 males; N = 22 females.
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fig-3: Scatter plot and linear regression between elytra length and left mandible for males and females.N = 29 males; N = 22 females.

Mentions: The rove beetles (Coleoptera: Staphylinidae) are a hyperdiverse family with more than 60,000 species described (unpublished database maintained by A Newton). Triacrus dilatus Nordmann belongs in the subtribe Xanthopygina, a monophyletic lineage of 29 neotropical genera, that includes some of the largest and most colorful of all rove beetles. While little is known about the behavior and natural history of xanthopygine beetles (Chatzimanolis, 2003; Chatzimanolis, 2014a), T. dilatus appears to have a fascinating natural history, occupying the nest refuse piles of the large paper wasp Agelaia vicina (de Saussure) in the Atlantic forests of Brazil, Argentina and Paraguay (Wasmann, 1902; Kistner, 1982). Adults and larvae of T. dilatus were seen feeding on fly larvae and breeding on the refuse piles of the paper wasp (Wasmann, 1902). While many details on the natural history of T. dilatus are still lacking, it is possible that T. dilatus exhibits the same behavior as Quedius (Velleius) dilatatus (Fabricius), a central European species also associated with paper wasps (Kistner, 1982). Both Q. dilatatus and T. dilatus have subserrate (asymmetrical, looking like marginal teeth-like structures pointing forward) antennae (visible on Fig. 3), which is often characteristic of rove beetles associated with social Hymenoptera (Schillhammer, 2013; Chatzimanolis, 2014b; Zhao & Zhou, 2015). According to zur Strassen (1957), Q. dilatatus is able to locate the paper wasps nests by following specific semiochemicals emitted by the wasps, and it is likely that T. dilatus can do the same.


Sexual dimorphism and allometry in the sphecophilous rove beetle Triacrus dilatus.

Marlowe MH, Murphy CA, Chatzimanolis S - PeerJ (2015)

Scatter plot and linear regression between elytra length and left mandible for males and females.N = 29 males; N = 22 females.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525698&req=5

fig-3: Scatter plot and linear regression between elytra length and left mandible for males and females.N = 29 males; N = 22 females.
Mentions: The rove beetles (Coleoptera: Staphylinidae) are a hyperdiverse family with more than 60,000 species described (unpublished database maintained by A Newton). Triacrus dilatus Nordmann belongs in the subtribe Xanthopygina, a monophyletic lineage of 29 neotropical genera, that includes some of the largest and most colorful of all rove beetles. While little is known about the behavior and natural history of xanthopygine beetles (Chatzimanolis, 2003; Chatzimanolis, 2014a), T. dilatus appears to have a fascinating natural history, occupying the nest refuse piles of the large paper wasp Agelaia vicina (de Saussure) in the Atlantic forests of Brazil, Argentina and Paraguay (Wasmann, 1902; Kistner, 1982). Adults and larvae of T. dilatus were seen feeding on fly larvae and breeding on the refuse piles of the paper wasp (Wasmann, 1902). While many details on the natural history of T. dilatus are still lacking, it is possible that T. dilatus exhibits the same behavior as Quedius (Velleius) dilatatus (Fabricius), a central European species also associated with paper wasps (Kistner, 1982). Both Q. dilatatus and T. dilatus have subserrate (asymmetrical, looking like marginal teeth-like structures pointing forward) antennae (visible on Fig. 3), which is often characteristic of rove beetles associated with social Hymenoptera (Schillhammer, 2013; Chatzimanolis, 2014b; Zhao & Zhou, 2015). According to zur Strassen (1957), Q. dilatatus is able to locate the paper wasps nests by following specific semiochemicals emitted by the wasps, and it is likely that T. dilatus can do the same.

Bottom Line: Linear regressions were run to examine if there were significant relationships between the different measurements.Our results indicated that males had significantly larger mandibles and ocular distances than females, but the overall body length was not significantly different between the sexes.We found no evidence of major and minor forms in either sex.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Tennessee at Chattanooga , Chattanooga, TN , USA.

ABSTRACT
The rove beetle Triacrus dilatus is found in the Atlantic forest of South America and lives in the refuse piles of the paper wasp Agelaia vicina. Adults of T. dilatus are among the largest rove beetles, frequently measuring over 3 cm, and exhibit remarkable variation in body size. To examine sexual dimorphism and allometric relationships we measured the length of the left mandible, ocular distance and elytra. We were interested in determining if there are quantifiable differences between sexes, if there are major and minor forms within each sex and if males exhibit mandibular allometry. For all variables, a t-test was run to determine if there were significant differences between the sexes. Linear regressions were run to examine if there were significant relationships between the different measurements. A heterogeneity of slopes test was used to determine if there were significant differences between males and females. Our results indicated that males had significantly larger mandibles and ocular distances than females, but the overall body length was not significantly different between the sexes. Unlike most insects, both sexes showed positive linear allometric relationships for mandible length and head size (as measured by the ocular distance). We found no evidence of major and minor forms in either sex.

No MeSH data available.


Related in: MedlinePlus