Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile Page: 64
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histories are most frequent at higher latitudes (i.e. 500N, 420S). For example, univoltine and
semivoltine life cycles have been described for aquatic insects inhabiting other Sub-Antarctic
islands, as in the case of the diving beetle Lancetes angusticollis (Curtis) (Coleoptera:
Dytisicidae), which exhibits a semivoltine life cycle in South Georgia, one of the coldest Sub-
Antarctic islands, with temperatures that range from -5 - 100C during the summer (Rodney and
Convey 1998). Furthermore, the stoneflies Notoperlafasciata and N. magnaspina (Plecoptera:
Gripopterygidae), exhibit semivoltine and merovoltine life cycles in Patagonian streams, where
temperatures range from 1 C- 120C (Beltran and Miserendino 2011). In our study, we were
able to determine that Gigantodax sp. (Diptera: Simuliidae) exhibits a life cycle that varies from
univoltine to multivoltine throughout a sharp altitudinal gradient typical of Cape Horn's
ecosystems. The presence of a multivoline life cycle could be explained through the lack of
seasonality experienced on most Sub-Antarctic islands in comparison with maritime and
continental Antarctic zones. This may be the most significant influence on the life history of
aquatic insects (Convey 1996) inhabiting these areas, where the summers are cool and the
winters are not specially cold (Danks 2007) due to oceanic damping. In this sense, cool
temperatures year-round, combined with a low or non-existent risk of extreme winter lows, could
allow for activity and development to be continuous (Convey 1996). Furthermore, as a result of
this limited seasonal variation, many Sub-Antarctic invertebrates show extensive overlap of
generations, often with little or no seasonal structure to the life cycle, and no true diapauses in
response to specific cues (Convey 1996).
Gigantodax sp. as an Indicator of Climate Change in South American Sub-Antarctic Streams
Although climate change and the increase in the predicted frequency of extreme climatic64
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Contador Mejías, Tamara Andrea. Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile, dissertation, December 2011; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc103303/m1/78/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .