Havaika
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| Havaika | ||||||||||||||||
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| Havaika jamiesoni Prószyński, 2002 |
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Havaika is a genus of the spider family Salticidae (jumping spiders). The genera Habronattus and Pellenes are closely related. All then known species were split from the genus Sandalodes (subfamily Plexippinae) (Prószyński, 2002).
All twelve species occur on the islands of the Hawai'ian and Marquesas chains. Recent molecular studies suggest that the species from the two chains are the result of independent colonizations (Arnedo & Gillespie, 2006).
Collecting travels in the late 1990 have suggested that the salticid fauna of Hawai'i has been drastically exterminated, so it may be that several or most of the described species are in fact already extinct.[1]
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[edit] Evolution on Hawai'i
The ancestors of modern Havaika species probably reached the Hawai'ian islands after most of the recent islands were already formed (about two million years ago), and after many other spiders had already colonized the islands. The speciation does not follow the progression rule typically found in radiated species of Hawai'i, where islands were colonized as they formed, creating new species on the way.
Four lineages can be discerned, using genetic analysis (Arnedo & Gillespie, 2006):
- Specimens from the pubens clade bear yellowish scales on the chelicerae in both sexes, and long palpal tibia in males. Their carapace is dark brown, with two lighter longitudinal dorsal bands. They occur on Maui, Moloka'i and Lana'i (which were once a single island), Kaua'i, O'ahu and Big Island.
- The verecunda clade shows sexual dimorphism: males bear rows of long white bristles on the chelicerae and have short palpal tibia, while females have few bristles, but dense white hairs on the clypeus. The black carapace sometimes sports a brush of white hairs on the mid-frontal part, with two longitudinal whitish spots. They occur on Moloka'i and Maui, which were a single island until about half a million years ago, Kaua'i and O'ahu.
- "Morphotype D" is almost uniformly dark brown with grayish longitudinal abdominal patterns. It shows sparse white scales restricted to the lower margin of the clypeus. It is found on Lana'i.
- H. cruciata shows the same facial characteristics as the verecunda clade, but can be distinguished by bulb characters. Males have a slender, long embolus originating from the basal half of the tegulum, similar to the embolus of the pubens clade, but a short palpal tibia. They have the same black carapace as the verecunda clade. H. cruciata is only found on Big Island. It is probably the sister taxon of Morphotype D.
- Specimens from Necker Island and Nihoa (northwest of Kaua'i) did not fit into the four defined morphotypes.
However, it is currently not feasible to group the poorly defined species into these lineages.
In all cases where two species were found on the same island, they significantly differed in size. This makes it likely that the two species hunt for different prey, and thus do not compete with each other. However, it seems that Havaika size differentiation happened soon after arrival on the Hawai'ian islands, with subsequent dispersal and further speciation. This is suggested by the observation that the bigger of two sympatric species always belongs to one evolutionary lineage (pubens clade), while the smaller belongs to the other (Arnedo & Gillespie, 2006).
[edit] Species
[edit] Marquesas group
- Havaika flavipes (Berland, 1933)
- Havaika nigrolineata (Berland, 1933)
- Havaika triangulifera (Berland, 1933)
[edit] Hawai'i group
- Havaika albociliata (Simon, 1900)
- Havaika canosa (Simon, 1900)
- Havaika cruciata (Simon, 1900)
- Havaika jamiesoni Prószyński, 2002
- Havaika pubens (Simon, 1900)
- Havaika navata (Simon, 1900)
- Havaika senicula (Simon, 1900)
- Havaika valida (Simon, 1900)
- Havaika verecunda (Simon, 1900)
[edit] References
- Prószyński, J. (2002). Remarks on Salticidae (Aranei) from Hawaii, with description of Havaika gen.n. Arthropoda Selecta 10(3): 225-241.
- Arnedo, M.A. & Gillespie, R.G. (2006). Species diversification patterns in the Polynesian jumping spider genus Havaika Prószyński, 2001 [sic] (Araneae, Salticidae). Molecular Phylogenetics and Evolution 41: 472-495. doi:10.1016/j.ympev.2006.05.012
- Platnick, N.I. (2007). The world spider catalog, version 7.5. American Museum of Natural History.
[edit] Further reading
- Proszynski, J. (2002): Personal working notes on Hawai'ian Salticidae Collection
