The Trichoptera

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  • Topic: Biogeography, Mercator projection, Tropics
  • Pages : 11 (3747 words )
  • Download(s) : 57
  • Published : March 30, 2013
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Introduction: The Trichoptera, or caddisflies, are an ecologically diverse order of insects. The adults resemble small moths and are terrestrial, while their larvae are aquatic and spin silk (Bongard 2004). It is due to their diverse designs in the secretion of silk threads that they are able to expand their ecological niches. The silk threads of the larvae are used to create shelters, nets, and cases- adopting an evolutionary system to exploit a wide range of resources (Vaughn 1985). There are about 10,000 species distributed world-wide, excluding Antarctica; displaying the varieties of niches that this order can occupy (Bongard 2004). Due to similarities between the adults, systematically, the Trichoptera are considered as the sister group of the order belonging to the butterflies and moths; the Lepidoptera (Bongard 2004). Their ancestral order is thought to have had a trichopteran-like adult, but the larva similar to a lepidopteran (Bongard 2004). In regards to the line leading to caddisflies, evolutionary adaptions have modified the larvae to be aquatic. Within the caddisfly families, two large, homogenous families- the Hydropsychoidea and Limnephiloidea- exist; with more primitive forms assigned a third, the Rhyacophiloidea (Bongard 2004). Those in the Limnephiloidea order contain families in which the larvae are able to construct portable cases with their silk and combinations of organic and inorganic materials (Bongard 2004, Vaughn 1985). The genus Helicopsyche, assigned to the family Helicopsychidae, belongs to the leptocerid branch of the Limnephiloidea (Bongard 2004). Members of the Helicopsyche are unusual and distinct due to their larval case. Constructed out of sand grains, the cases superficially resemble spiraled snail shells; in a helical form (Vaughn 1985). Due to its distinct feature that is found rarely outside the family, distributions records are relatively comprehensive. With such available research and data, the current global distribution of the Helicopsyche genus can be examined in terms of distribution patterns.

Materials & Methods: Scientific literature on helicopsychids was made available through journal articles, chapters from books, and identification keys. The literature was used to extract information on the global distribution of the Helicopsyche genus. The different species and fossil species of Helicopsyche were noted, as well as their region(s) of occurrence; being the country or area that they reside in and as the biological realm in which they exist. This information was used to construct a table where the species are listed and organized as they exist within the six major biological realms being Australian, African, Oriental, Palearctic, Nearctic and Neotropical. This data was then plotted on Mercator projection maps of the world; showing the distribution within the realms visually. In determining the distribution of the Helicopsyche genus, endemicity is highly relevant. This was determined through the construction of locality cladograms based on shared species. From the data of the cladograms, species complexes were constructed from the disconnected bits, and further connections were made on the complexes. Through the data obtained from the literature, tables, Mercator maps and cladograms, further hypotheses between the distributions of the Helicopsyche genus and their origins were made and observed.

Results: From the available literature, 95 species from the Helicopsyche genus were discovered and categorized according to regions of locality. From their regions, further organizations were made according to the Biological Realm that their region belongs to. Further comparisons were done through the plotting of information on Mercator projection maps of the world. Finally, a locality cladogram was constructed to make further observations of their distribution patterns and species complexes. In Table 1, all the 95 species of the Helicopsyche genus are listed and organized...
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