First record of fossil insects from the middle holocene of Tierra Del Fuego, Argentina

RAMÍREZ, LEONARDO C.; ALONSO, CECILIA P.; NEGRE, JOAN

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2017 vol. 54 p. 713 - 719

0002-7014

WHILE the astonishing growth of the knowledge of Quaternary Paleoentomology during the last decades continues toaccelerate, contributions related to the austral region ofSouth America have only been made about Chilean territory.In this context, Ashworth, A.C., and Hoganson, J.W. werepioneers in the study of Quaternary fossil insect associationsby studying several Late Pleistocene and Holocene insectfaunas in the coastal region of central and southern Chile.For example, in 1989, they examined the peat depositsof the archaeological site Monte Verde (Ashworth et al.,1989); during 1987 (Ashworth and Hoganson, 1987), theyanalyzed the deposits of Río Caunahue and conducted alarge-scale survey of extant insect communities in thePuyehue National Park. In the early 90?s, they summarizedtheir work with Late Pleistocene insect associations ofPuerto Octay, Puerto Varas and Río Caunahue (Hogansonand Ashworth, 1992). Finally, Ashworth (2007) studied theinsects from the peat deposits of Lago Rupanco and theoutcrops of Dalcahue at Chiloé Island. At higher latitudes,Ashworth and Markgraf (1989) and Ashworth et al. (1991)studied the Late Pleistocene and Holocene faunas of TémpanoSur and Puerto Edén. Ashworth et al. (1997), and subsequentlyAshworth and Kuschel (2003), mentioned thepresence of fossil weevils (Curculionidae) in Antarctica.On the other hand, regarding the southern regions of Argentina,an early?middle Holocene fossil insect assemblagehas been reported from Islas Malvinas, Argentina (Bucklandand Hammond, 1997). Studies from the Argentinean Patagonia(e.g., Ariztegui et al., 1997; Massaferro and Corley,1998; Bianchi et al., 1999; Massaferro et al., 2004) are mainlyfocused on the paleolimnological implications of entomologicalstudies and based on Chironomidae (Diptera). Quaternaryfossil insects have been mentioned in some studies(e.g., Pardiñas et al., 1998; Petrulevičius, 1999; Voglino andPardiñas, 2005), but only recent works have focused onthem (e.g., Ramírez and Alonso, 2014; Ramírez and Alonso,2016; Ramírez and Michat, 2016; Ramírez et al., 2016).Globally, most of the Quaternary fossil insects are extractedfrom peat deposits (Grimaldi and Engel, 2005). Thatinformation becomes highly relevant when consideringthat about 95% of the area covered by peatlands in Argentinais located in Tierra del Fuego, mainly at the bottom ofthe southern valleys in Isla Grande (Iturraspe, 2010). Withan average accumulation rate of 0.51 to 0.93 mm/yr duringthe Quaternary (Rabassa et al., 1989), the Fuegian peatlandsare a real database almost continuously recording informationrelated with the environmental conditions and theweather in the region.In addition to numerous palinological studies on the Islandof Tierra del Fuego (e.g., Heusser, 1995, 2003; Borromeiand Quattrocchio, 2008; Ponce et al., 2010), other bioproxies,such as ostracods (Cusminsky et al., 2011), mollusks (Candelet al., 2009), marine microflora (Rabassa et al., 2009),calcareous macro and microfossils (Gordillo et al., 2010), anddiatoms (Fernández et al., 2012), were used to infer the environmentalconditions and weather during the Quaternary.Even for Patagonia, fossil assemblages of mammals (Tonniand Carlini, 2008), fish and penguins (Cione et al., 2011), reptiles(Albino, 2011), and land birds (Tambussi, 2011) werestudied with the same purpose.Paleoclimatic data obtained from classical biomarkershas not yet led to the precise definition of climate changeduring the Quaternary. Insects differ from other bioproxiesin the degree of detail of the environmental informationthey provide. Most bioproxies can only be identified at thegenus or family level, while insects can often be identified tothe species level.In this work, we present the remains of Migadops latus,the first fossil insect extracted from the peatlands of Tierradel Fuego. The Migadopini are a small group of Carabidaethat occur in southern South America, Australia, New Zealand,the circum-Antarctic islands (Jeannel, 1938) and in thenorth Andean region of South America (Moret, 1989). Inaddition, it constitutes a characteristic element of the sub-Antarctic biota and, except for some common species likeM. latus, its specimens are usually very rare in collections.Jeannel (1938) made the only comprehensive review of thetribe; later, Straneo (1969) and Nègre (1972) added newspecies whereas Baher (1997) added subspecies and Moret(1989) a new genus.The genus Migadops Waterhouse, 1842 is distributedthroughout the southern tip of America, including Tierra delFuego and Islas Malvinas (Reichardt, 1977); it includes onlytwo species, both present in sub-Antarctic environments(Roig-Juñent and Dominguez, 2001). Migadops latus is themost abundant species on the southern fringe of Tierradel Fuego, Chile and Argentina (Niemelä, 1990). Adults areregistered from December to February and show a preferencefor humid environments (Elgueta et al., 2013). This findingis the first step in the characterization of the Quaternarypaleoentomofauna of Tierra del Fuego and sets the beetlesas bioproxies for paleoclimatic studies in the southernmostarea of South America.