Anelosimus

Anelosimus
female A. crassipes from Japan
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Suborder: Araneomorphae
Family: Theridiidae
Genus: Anelosimus
Simon, 1891
Species

see text

Diversity
52 species

Anelosimus is a cosmopolitan genus of cobweb spiders (Theridiidae), currently containing 64 species. Anelosimus is a key group in the study of sociality and its evolution in spiders (Aviles 1997). It contains species spanning the spectrum from solitary to highly social (quasisocial), with eight quasisocial species, far more than any other spider genus. Among these is the South American social species Anelosimus eximius, among the best studied social spider species.

The web of a colony of A. eximius can reach cover entire tree canopies and contain tens of thousands of individuals. Most of the highly social species live in lowland tropical forests, and all occur in the Americas. Other species, particularly those at higher altitudes in northern latitudes in the Americas - and all non-American species -, appear to be solitary or sub-social. [1][2] Social Anelosimus species are generally highly inbred and have female-biased sex ratios, with up to 10 females per male.

The social, subsocial, and solitary behavior of differing species within Anelosimus has been used to examine hypotheses of environmental pressures on social behavior, and inbreeding.[3] Subsociality as a trait seems to be conserved, despite the wide range of environments in which Anelosimus species live; all known solitary species within the genus belong to a single clade.[4] Sociality, however, has independently arisen several times.[3]

Description

Anelosimus spiders have a notched red or brown band on their abdomen, which is dark when preserved in alcohol. Laterally, the abdomen has a white band and/or white blotches. Specimens range in size from 1.8 to 7.5 millimetres (0.071 to 0.295 in). Individuals in this genus lack a colulus.[5]

Species

male A. crassipes
female A. exiguus
male A. exiguus

References

Wikimedia Commons has media related to Anelosimus.
  1. ↑ Agnarsson, Ingi (2012). "Systematics of new subsocial and solitary Australasian Anelosimus species (Araneae: Theridiidae)". Invertebrate Systematics 26: 1–16. doi:10.1071/is11039.
  2. ↑ Powers, K.S.; Aviles, L. (2007). "The role of prey size and abundance in the geographical distribution of spider sociality". Journal of Animal Ecology 76 (5): 995–1003. doi:10.1111/j.1365-2656.2007.01267.x. PMID 17714278.
  3. 1 2 Agnarsson-Avile, I.; Avilés, L.; Maddison, W.P. (2013). "Loss of genetic variability in social spiders: genetic and phylogenetic consequences of population subdivision and inbreeding". Journal of Evolutionary Biology 26 (1): 27–37. doi:10.1111/jeb.12022. PMC 3588177. PMID 23145542.
  4. ↑ Agnarsson, Ingi; Kuntner, Matjaz; Coddington, Jonathan; Blackledge, Todd (2010). "Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae)". Zoologica Scripta 39: 75–87. doi:10.1111/j.1463-6409.2009.00406.x.
  5. ↑ Agnarsson, Ingi (2006). "A revision of the New World eximius lineage of Anelosimus (Araneae, Theridiidae) and a phylogenetic analysis using worldwide exemplars". Zoological Journal of the Linnean Society 146 (4): 453–593. doi:10.1111/j.1096-3642.2006.00213.x.

World Spider Catalog. 2015. http://www.wsc.nmbe.ch/

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