Search

En este capítulo se presenta el uso de los quironómidos como paleoindicadores ambientales en la región Neotropical, discutiéndose aspectos relativos a las variables que se pueden reconstruir en base a este grupo de insectos, a los sectores geográficos que han sido cubiertos por estos estudios a las interrogantes respecto del pasado climático, que estos estudios pueden ayudar a responder y a los estudios futuros que pueden realizarse en esta temática en diferentes subzonas de la región Neotropical. Fil: Massaferro, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina Fil: Araneda Castillo, Alberto Eduardo. Universidad de Concepción; Chile Fil: Motta, Luciana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina

Alotanypus vittigera (Edwards, 1931), comb. nov. Anatopynia vittigera Edwards 1931: 242 ���243, fig. 36 b; Spies & Reiss 1996: 82 (listed as unplaced valid species). Type material (all in NHM). HOLOTYPE male (NHM) L. Nahuel Huapi, Eastern end, R��o Negro province, Argentina, 28���31.x. 1926, F.W. Edwards. Paratypes. 3 males and 2 females same date as holotype; 1 male and 2 females, L. Correntoso, R��o Negro province, Argentina, 18���25.xi. 1926, F.W. Edwards; 1 male, Bariloche, R��o Negro province, Argentina, 25���28.xi. 1926, F.W. Edwards; 1 male, Puerto Montt, Llanquihue province, S. Chile, 24.xii. 1926, F.W. Edwards. Recently collected material. 1 male and 2 females from 41 ��00��56 ����S, 71 �� 49��54 ����W, 856 m, Mall��n La Heladera, Puerto Blest, PNNH, R��o Negro province, Argentina, 07.i���04.ii. 2007, Garr�� & Montes de Oca, Malaise trap, and 3 fourth instar larvae from same site, 04.ii. 2007, Garr�� & Montes de Oca, Kick sample; 4 males with their pupal exuviae and 2 females with their pupal exuviae (all adults emerged same day of collection) from 41 �� 36��06����S, 71 �� 36��25 ����W, temporary pool beside Vertiente stream, Manso Inferior, PNNH, R��o Negro province, Argentina, 10.i. 2008, G. Orpella; 1 male with its pupal exuviae (adult emerged on 12.ii. 2009), 2 females with their pupal exuviae (both adults emerged on 11.ii. 2009), 1 prepupa and 2 fourth instar larvae, 41 ��00��05����S, 71 �� 50��53 ����W, 855 m, Mall��n La Heladera, Puerto Blest, PNNH, R��o Negro province, Argentina, 11.ii. 2009, A. Siri, kick sample. Emended diagnosis. The diagnosis of Alotanypus vittigera (Edwards) comb. nov. should be emended as follows: Male: vittae strongly or not indicated; AR lesser or slightly higher than 2.0; anepisternals, preepisternals and postnotals present or absent; LR I = 0.60���0.75. Pupa: Thoracic seta DC 1 shorter or longer than DC 3. Descriptions. Male (n = 5���12, except when otherwise stated) (Figs. 1���8) Total length 5.15���6.23 mm. Total length / wing length 1.61���1.89. Coloration: Thorax yellowish brown to dark brown, with or without evident vittae. Anepisternum, preepisternum and postnotum dark brown; abdomen as Fig. 1. Wing with several dark spots on membrane; macrotrichia above dark spots thick and densely grouped; central section of Cu, cross-veins RM and MCu, FCu and basal section of M 3 + 4 darkened (Fig. 2). Head: Antenna; AR 1.9���2.1 [1.95]. Temporals multiserial 42���76 [71]; postorbitals bi to multiserial, 21���26 [21]. Clypeus with 7���20 [11] setae. Tentorium 257���274 [270] long (4). Palpomere lengths (1���5) 59���84 [70]; 101��� 148 [145]; 153���195 [150]; 227���282 [250]; 315���415. Thorax. Antepronotum with 12���19 [17] lateral setae; humerals 14 (1); acrostichals biserials between vittae, diverging as uni to multiserial, merging with the dorsocentrals in the prescutelar area; dorsocentrals 44 (1); prealars 26���38 [35]; supraalar 1; anepisternals 0���3 [3]; scutellars 35���86 [76]; postnotum with 0���10 [0]; preepisternals absent. Wing with macrotrichia in all cells except to r 1 and r 2 + 3; length 3.10���3.80 [3.30] mm; width 0.90���1.06 [0.93] mm. L / W = 3.26���4.12 [3.55]. VR 0.88���0.97 [0.94]. C extended beyond R 4 + 5. Brachiolum with 4���8 distal setae, plus 4���5 proximal setae. Squama fringed with up to 65 setae. Legs. Tibial spur on p 1 with slightly curved apex, 102���116 [113] long; comb on p 1 with 9���13 [10] short spines (Fig. 3). Tibial spurs on p 2 95���120 [115] and 63���83 [75] long (Fig. 4). Tibial spurs on p 3 91���120 [113] and 69���81 [75] long (Fig. 5); spur ratio 0.65���0.74 [0.66]; comb on p 3 with 10���12 [12] spines, the outer slightly "S" curved (Fig. 6). Two pseudospurs on ta 1���2 of p 2 and ta 1 of p 3. Lengths and proportions of legs in Table 3. fe ti ta 1 ta 2 ta 3 p 1 1307���1563 [1540] 1652���1880 [1750] 1224���1351 [1200] 625���717 [625] 415���497 [463] p 2 1452���1629 [1588] 1593���1805 [1750] 1017���1152 [1063] 525���612 [525] 350���418 [350] p 3 1245���1468 [1325] 1780���2095 [2000] 1328���1544 [1413] 665���795 [725] 428���530 [475] continued. ta 4 ta 5 LR BV SV p 1 259���327 [275] 172���226 [200] 0.68���0.76 [0.69] 2.65���2.93 [2.87] 2.38���2.74 [2.74] p 2 208���249 [225] 165���200 [200] 0.60���0.66 [0.61] 3.13���3.39 [3.39] 2.91���3.17 [3.14] p 3 268���324 [288] 180���207 [200] 0.68���0.76 [0.71] 2.59���2.96 [2.81] 2.27���2.52 [2.35] Hypopygium (Fig. 7). Setae on tergite IX, 17���24. Gonocoxite 249���291 [280] long. Gonostylus 135���161 [145] long. Aberrant specimens (3) with a very thick megaseta-like lateral to the megaseta; 1 aberrant specimen with the very thick megaseta-like, plus 1 additional strong spine (Fig. 8). HR 1.65���2.04 [1.93]; HV 1.97���2.41. Female (n = 5���7, except when otherwise stated) (Figs. 9���11) Total length 4.50���5.15 (4). Total length / wing length 1.27���1.44 (4). Coloration: Thorax and wing spots as in male; cercus yelowish. Head. Antenna with 14 flagellomeres, AR 0.21���0.23 (4). Temporal setae multiserial, 74 (1), postorbitals bi to multiserial, 45 (1). Clypeus with 16���21 setae. Palpomere lengths (I���V) 70���90; 102���150; 150���200; 220���303; 210 (1) long. Thorax. Antepronotum with 15���26 lateral setae and 0���4 dorsal setae. Acrostichals as in male; prealars 33���55; supraalar 1; anepisternals 1���6 (4), scutelars 86���118. Preepisternals and postnotals absent. Wing with macrotrichia in all cells except to r 1 and r 2 + 3; length 3.40���3.70 mm; width 1.16���1.50 mm; L / W = 2.39���2.90. VR 0.92���0.97. C extended beyond R 4 + 5. Squama fringed with 60���87 setae. Macrotrichia above dark spots thick and densely grouped Legs. Tibial spur on p 1 95���120 long; on p 2 93���128 and 66���88 long; on p 3 93���120 and 73���83 long. Spur ratio on p 3 0.65���0.78. Comb on p 3 with 9���12 spines; no tibial comb on p 1. Two pseudospurs on ta 1���3 of p 2 and ta 1 of p 3. Lengths and proportions of legs in Table 4. Genitalia (Fig. 9). Cercus 81���125 long. Seminal capsule 91���125 long (Fig. 10); notum 216���300 long (2); tergite IX with 0���5 setae (3) (Fig. 11); segment X with 6���13 setae (4). Pupa (n = 4���9, except when otherwise stated) (Figs. 12���17) Total length 6.25���8.30 mm. Cephalothorax (Fig. 12). Frontal apotome as in Fig. 13. Thoracic horn (Fig. 14) arising from a distinct tubercle; external membrane with spines; respiratory atrium almost straight. Length 524���596; width 106���135; L / W 4.41��� 4.95; plastron plate 58���85 long; 97���132 wide; plastron plate length / thoracic horn length 0.11���0.15. Thoracic setation (Fig. 15): DC 1 41���54; DC 3 95���140; Sa 203 long (1); MAps 175���188 long (2). Abdomen. Scar on segment I, 216���249 long. Shagreen with single spines. Chaetotaxy (Figs. 16, 17): D 1 more or less straight, arising from a distinct tubercle on segments I���VII. D 1 is situated in the same line or slightly posteriorly to D 2 in segments VI and VII. D 2 and D 4 longer than D 1, arising from a distinct tubercle in segments II���VII. D 3 and D 5 short and thin, arising from a very short tubercle or tubercle absent. Segments I���VI with two pairs of FIGURES 12���26. Alotanypus vittigera (Edwards) comb. nov. immatures. Pupa: 12, cephalothorax; 13, frontal apotome; 14, thoracic horn; 15, thoracic setae: Dc 1, Dc 2 and Sa from left to right; 16, complete abdominal setation; 17, tergite and sternite of abdominal IV segment. Fourth-instar larva: 18, ventral cephalic setation; 19, dorsal cephalic setation; 20, antennite I; 21, apex of antenna; 22, mandible; 23, ligula; 24, dorsomental teeth; 25, procercus; 26, simple claws of posterior parapod. Scale bars = 20 ��m for Fig. 21; 50 ��m for Figs. 13, 24, 26; 100 ��m for Figs. 12, 15, 20, 22, 23, 25; 200 ��m for Figs. 14, 17; 500 ��m for Fig. 16. short lateral setae. Segments VII and VIII with 5; anal lobe with 2 pairs of long and teniated lateral setae. Position of LS 1 / segment length = 0.45���0.51 on segment VII; 0.22���0.27 on segment VIII. Anal lobe 803���996 long; 400��� 450 wide; L / W 1.93���2.05. Position of LS / anal lobe length 0.16���0.18 for LS 1 and 0.27���0.28 for LS 2. Male genital sac 355���387 long; length of male genital sac / length of anal lobe 0.42���0.44. Fourth-instar larva (n = 5���6, except when otherwise stated) (Figs. 18���26) Total length 0.77���0.91 mm (2). Head: capsule 620���800; 820���1000 wide. CI 0.76���0.85. Cephalic setation: Ventral (Fig. 18): SSm between S 9 and S 10;SSm close to S 10 and VP posterior to S 10. Dorsal (Fig. 19): S 7, S 8 and DP arranged in a line; S 6 anterolateraly to S 7. Antenna (Figs. 20, 21). AR 4.9���5.6; A 1 233���266 long, ring organ situated at 0.70���0.76 from base; BL 1 35���42 long; NB 33���37 long; NB / BL 1 0.83���0.90; BL 1 / A 2���4 0.80���0.88; A 2 28���35 long, length A 2 / width A 2 4.3���6.6 (3); BL 2 10���11; A 3 7���11 long; length A 3 / width A 3 3.6���4.4; A 4 5 long. Maxillary palp: basal segment 60���73 long, length / basal width 0.59���0.67; relative distance of CS 0.59���0.67. A 1 / PMx 3.64���4.08. Mandible (Fig. 22) 191���213 long. A 1 / Mn 1.17���1.26. Hypopharingeal complex: Ligula 108��� 145 long (Fig. 23), the outermost inner teeth slightly outcurved; paraligula bifid, 60���95 long; pecten hypopharyngis with 14���18 teeth; dorsomental teeth 5���7 (Fig. 24). Abdomen. Procercus 250���350 long (Fig. 25); L / W 3.00��� 3.50; with 13 setae 855���1050 long. Preanal seta 780��� 830 long. Posterior parapods: smallest claws simple curved (Fig. 26). Biology. The species A. vittigera was found in a wide range of standing water environments such as lakes, temporary pools and ���mallines��� (singular ���mall��n���). A ���mallin��� can be characterized as a humid meadow with a dense cover mainly dominated by Juncaceae, Cyperaceae and Gramineae. The mall��n soil contains a high percentage of organic matter and always associated with either surface water or ground water discharge. This kind of wetland in the Andes mountains is characterized by harsh environmental conditions, as the plant growth season is relatively short (abouth 4 months) and snow cover remains for about 6 months during the year (Raffaele 1996). Cladistic analysis. The data set analyzed under K = 5 to 16 yielded the same tree topology (Fig. 27) in each of the concavities (CI = 0.47, RI = 0.42). The tree derived from K = 5 (score = 30.37) showed the best character measure support calculated as absolute frequencies, frequency differences and absolute Bremer support. The best relative Bremer support measures were those of K = 7 (score = 29.7). The genus Alotanypus is a monophyletic group supported by the synapomorphies male AR of 1.8, male LR III of 0.68���0.76, female wing length of 3.30���4.20 mm, L / W of thoracic horn 3.00��� 4.60, relative position of LS 1 on segment VII of 0.51, relative position of LS 1 on segment VIII of 0.23���0.31, CI of 0.83���0.84, postnotal setae absent, tibial comb I present, claws spatulate (at least on pII). Alotanypus venustus is the basal species of the genus followed by A. dalyupensis and A. aris. The species A. vittigera is closely related with A. kuroberobustus and shares the characters male AR of 1.90���2.10, male wing length of 3.10���3.80, male LR II of 0.60���0.66, female LR II of 0.53���0.61, L / W of thoracic horn of 4.30���5.50, relative position of LS 1 on segment VII of 0.45���0.51, NB / BL 1 of 0.77 and curved apex of spur I on male. The clade [A. aris - A. vittigera - A. kuroberobustus] shares the characters female LR III of 0.63���0.71, DC 1 of 54��� 58 um long, thoracic horn of 524���680 um long, larval AR of 5.30���6.40, BL 1 / A 2���4 of 0.80���0.88, A 1 / Ring 0 of 0.70���0.76 and L / W PMx of 2.75���3.30. The clade [A. dalyupensis - A. aris - A. vittigera - A. kuroberobustus] shares the characters DC 1 of 78 um long, plastron plate / thoracic horn of 0.15���0.33, L / W of anal lobe of 1.82, L / W of A 2 of 4.50, relative position of CS on PMx of 0.50, mandible of 191���220 um long, A 1 / mandible of 1.19���1.29 and procercus of 296 um long. Guassutanypus oliveirai is the sister group of Alotanypus. This clade shares the presence of preepisternals, RM, FCu and MCu darkened veins on male and female, assymetrical neck position on seminal capsules, relative position of LS 1 on abdominal segment VII, horn sac of the thoracic horn not filling the entire horn lumen, number of teniated setae on segment VIII on pupa. This last clade is the sister group of the clade [P. d y a r i -D. alaskensis] by sharing characters: LR I on male; FCu vein darkened in male and female; length of DC 3 on pupa, A 1 / PMx, pecten hypopharnix and number of setae on procercus. The tribe Macropelopiini is monophyletic and it is supported by the synapomorphies male wing length of 3.00, male spur ratio of 0.28���0.42, female anal lobe length of 695���864, genital sac / anal lobe of 0.36���0.42, relative position of 0.16���0.17 for LS 1 and 0.25���0.26 for LS 2 on anal lobe, larval AR of 6.05 ���7.00, L / W PMx of 2.70, procercus length of 163���222, postorbitals multiserials, male spur thorn like. Spur teeth bigger than 15, outer fringed on anal lobe present and teniata setae on abdominal segment VII bigger than 5., Published as part of Siri, Augusto, Donato, Mariano, Orpella, Germ��n & Massaferro, Julieta, 2011, Alotanypus vittigera (Edwards) comb. nov.: adult redescription, immature description and a phylogenetic analysis of the genus (Diptera: Chironomidae: Tanypodinae), pp. 46-64 in Zootaxa 2795 on pages 54-61, DOI: 10.5281/zenodo.204609, {"references":["Edwards, F. W. (1931) Chironomidae. In: Diptera of patagonia and South Chile. Part II, Nematocera. Trustees of the British Museum (Natural History), London, pp. 233 - 331.","Spies, M. & Reiss, F. (1996) Catalog and bibliography of Neotropical and Mexican Chironomidae (Insecta, Diptera). Spixiana, Supplement, 22, 61 - 119.","Raffaele, E. (1996) Relationships between seed and spore banks and vegetation of a mountain flood meadow (mallin) in Patagonia, Argentina. Wetlands, 16, 1 - 9."]}

Parakiefferiella claviculata (Edwards, 1931), comb. n. Spaniotoma (Eukiefferiella) claviculata Edwards, 1931: 291. Parakiefferiella lagorum Wiedenbrug & Andersen, 2002: 120, syn. n. The measurements obtained by the study of the type material were carefully compared with the description of P. la go ru m made by Wiedenbrug & Andersen (2002) and it fits exactly with all of them. Therefore, a re-description or an emendation of that diagnosis is not needed. Material examined: Holotype male (NHM), Argentina, Terr. R��o Negro, L. Nahuel Haupi Eastern End, 28 / 31 ���X��� 1926, leg. F. & M. Edwards, B.M. 1927 ��� 63; paratype male (NHM), same data as holotype., Published as part of Massaferro, Julieta, Donato, Mariano & Brooks, Stephen J., 2009, New placement for Spaniotoma (Eukiefferiella) claviculata Edwards, 1931 (Diptera: Chironomidae), pp. 67-68 in Zootaxa 2125 on page 67, DOI: 10.5281/zenodo.188250, {"references":["Wiedenbrug, S. & Andersen, T. (2002) New species of Parakiefferiella Thienemann, 1936 from South America (Chironomidae, Orthocladiinae). Studies on Neotropical Fauna and Environment, 37 (2), 119 - 132"]}

La familia Chironomidae (Diptera: Nematocera) es uno de los grupos de insectos más ampliamente distribuidos y abundantes en cuerpos de agua dulce. Los representantes de esta familia pueden explotar áreas con amplios gradientes ambientales. La información que se presenta está basada en la recopilación de datos distribucionales bibliográficos, del estudio del material tipo de las especies de Chironomidae depositadas en el Natural History Museum (UK) y del material de colección del Museo de La Plata (Argentina). En la Patagonia, se registran 9 subfamilias, la subfamilia monotípica Chilenomyiinae es endémica de esta área. Dentro de estas subfamilias, 53 de los 111 géneros conocidos para América del Sur están presentes en la Patagonia. Del total de géneros de la Patagonia, el 20 % es endémico y 7 de ellos muestran relaciones transantárticas. En la Patagonia, se registran 177 especies de Chironomidae, el 98% de éstas son endémicas, el 3 % son consideradas nomina dubia y el 17% requiere revisión ya que su ubicación sistemática es dudosa. Las descripciones originales de las especies patagónicas de Chironomidae están basadas principalmente sobre machos (n=58) y machos y hembras (n=43), ambas representan el 57% del total; el resto de las especies han sido descriptas con diferentes combinaciones de estadios del ciclo de desarrollo., The Chironomidae (Diptera: Nematocera) family is one of the most widely distributed group of insects and often the most abundant in freshwater environments. Representatives of this family can exploit a wide range of environmental gradients. The information here presented is based on the compilation of distributional data obtained from bibliography, the study of the type material deposited in the Natural History Museum (UK) and the collection material from Museo de La Plata (Argentina). Nine subfamilies are recorded from Patagonia, being the monotypic subfamily Chilenomyiinae endemic for the area. From the 111 known genera from South America, 53 are present in the studied area. Aproximately 20 % of the genera recorded from Patagonia are endemic and 7 of them have transantarctic relationships. In Patagonia there are 177 species of Chironomidae, out of which 98% are endemic, 3 % are considered nomina dubia and ca. 17 % requires revision since their systematic position is doubtful. The original descriptions of the chironomid species from Patagonia are based mainly on males (n=58) and males and females (n=43) both amounting to 57 % of the total, the rest of the species have been described using different combinations of stages from their life cycle., Facultad de Ciencias Naturales y Museo, Consejo Nacional de Investigaciones Científicas y Técnicas

Las reconstrucciones paleoambientales y paleoclimáticas a partir de indicadores (proxies) archivados en los sedimentos acumulados en los lagos, permiten conocer la dinámica de estos ecosistemas y la respuesta de los mismos frente a la variabilidad ambiental pasada a distintas escalas que van desde milenios a decenios de años. Los cambios en el clima y la actividad antrópica son las principales forzantes de cambio en los ambientes lacustres. Los restos subfósiles de las larvas de quironómidos (Diptera: Chironomidae) son útiles paleoindicadores (paleoproxies) biológicos porque responden a los cambios en las condiciones ambientales del pasado. Además, son utilizados en estudios multiproxy ya que proveen información independiente que, combinada con otros proxies, genera una respuesta integrada de las condiciones ambientales que reinaron en el pasado. Los últimos estudios paleolimnológicos del norte de la Patagonia y centro de Argentina indican la existencia de un contraste regional en cuanto a precipitaciones y temperaturas que se evidencia a lo largo de la Diagonal Árida Argentina. Esta franja escinde dos grandes conjuntos de sistemas lacustres con diferente regulación hídrica y con respuesta paleohidrológicas contrarias frente a fases climáticas conocidas, como por ejemplo la Pequeña Edad de Hielo. El objetivo principal de esta tesis fue estudiar las variaciones ambientales (naturales y antrópicas) registradas durante los últimos ca. mil años a ambos lados de la Diagonal Árida (DA) con el fin de aportar nuevas evidencias del contraste climático regional (anti-fase). Para ello se estudiaron y compararon los ensambles de quironómidos subfósiles contenidos en secuencias sedimentarias lacustres ubicadas a un lado y otro de la DA. Las secuencias sedimentarias seleccionadas fueron Laguna la Barrancosa (37° S) en el suroeste de la provincia de Buenos Aires, región Pampeana y Lagunas Verde y Toncek (41° S) en el noroeste de Patagonia. Para reconstruir la historia ambiental de cada laguna y relacionarla con los eventos climáticos de los últimos 1000 años, se incorporó información provista por otros proxies sedimentarios como los pigmentos fotosintéticos fósiles (derivados de clorofila y carotenoides totales), la materia orgánica y en los casos que fue posible, información geoquímica (N, C, S) y de ostrácodos. Los resultados obtenidos en cada secuencia sedimentaria a partir de los indicadores estudiados permitieron definir diferentes intervalos de tiempo o períodos con distintas condiciones ambientales. Se definieron 3 períodos climáticos en la historia ambiental de la laguna La Barrancosa: Un primer período oscilante entre condiciones secas y húmedas, entre ~610-1278 AD, coincidentes en parte con la Anomalía Climática Medieval; un segundo período, entre ~1278-1947 AD dominado por condiciones más secas asociada al período la Pequeña Edad de Hielo; y finalmente un tercer período, el más actual, entre 1947-2012 AD, dominado por condiciones húmedas en su primera parte y coincidente con el Salto Climático del siglo XX. La dinámica ambiental, en la historia más reciente de la laguna ubicada en el suroeste de la provincia de Buenos Aires, estuvo marcada por una fuerte impronta de las actividades antrópicas en la región y por el incremento de las precipitaciones con inicio en la década del 1940. Durante el siglo XV, se infirió el establecimiento de un ambiente temporal sub-salino y un balance hidroclimático negativo. Durante la década de 1970, La Barrancosa se habría establecido como una laguna permanente en estado trófico “claro”, asociado al incremento en las precipitaciones regionales (Salto Climático del siglo XX) y al cambio ecológico regional que impulsó el cambio en los patrones de circulación y precipitaciones de esa región. Desde 1990, los procesos de eutrofización en la laguna se aceleraron, probablemente como consecuencia del incremento en la actividad agrícola que registró el área y por el uso de técnicas agrícolas modernas basadas en el uso intensivo de fertilizantes y pesticidas. Otras actividades como la siembra de la especie Odontesthes bonariensis, podría haber favorecido los procesos de eutrofización en la laguna. En la Laguna Verde se definieron 3 períodos climáticos diferentes: el primero de ellos entre ~1561-~1670 AD dominado por condiciones frías y húmedas coincidente, en parte, con el transcurso de la Pequeña Edad de Hielo en Patagonia; un segundo período ~1670- ~1878 AD dominado en su última parte por condiciones mayormente secas; y por último el tercer período, el más actual entre ~1878-2012 AD coincidente en su última parte con el calentamiento global del siglo XX registrando condiciones climáticas más cálidas que en el período anterior. Por último el registro sedimentario de la laguna Toncek, permitió definir 2 períodos climáticos, el primero de ellos (~1644-1960 AD) dominado mayormente por condiciones frías. En la primera parte de este período y hasta ~ 1870 AD habrían dominado condiciones húmedas y frías coincidente también con el transcurso de la Pequeña Edad de Hielo. Y un segundo período 1960 AD-2012 AD, coincidente con el calentamiento global del siglo XX que habría permitido un leve incremento en la productividad de la lagunas. Las importantes diferencias en cuanto a riqueza y abundancia que se observan en los registros de quironómidos subfósiles de las lagunas Verde y Toncek, se relacionan principalmente a condiciones locales (ubicación por encima y por debajo de la línea de crecimiento arbóreo, tipo de cuenca cerrada o abierta, presencia o ausencia de macrófitas) que, entre otras diferencias, definen la contribución de material orgánico, con gran impacto en la dinámica del ambiente y en la composición faunística. En términos generales, las paleocomunidades de quironómidos de cada ambiente reflejaron cambios importantes en su composición y abundancia frente a eventos climáticos, hidrológicos y antrópicos ocurridos durante los últimos 1000 años en el sudoeste de la provincia de Buenos Aires y últimos 500 años en el sector noroeste de Patagonia. Sin embargo, en todos los registros los cambios más notorios se evidenciaron en los últimos 100 años de la historia evolutiva de cada laguna y particularmente en los ambientes del Noroeste de Patagonia por el impacto recurrente de caída de cenizas en el área, proveniente del área cercana chilena durante los últimos 200 años. Las reconstrucciones paleoambientales efectuadas a un lado y otro de la DA permitieron observar patrones de respuesta opuestos en cuanto a cambios en los niveles de agua y productividad durante el período climático frío denominado Pequeña Edad de Hielo. Los cambios hidroclimáticos de los últimos 1000 años, fueron más notorios en el ambiente pampeano, Laguna La Barrancosa, ubicado en el suroeste de la provincia de Buenos Aires. Por otro lado en todos los registros, se observaron cambios de productividad en los últimos 100 años, los cuales estarían asociados a una combinación de 1) aumento de temperatura durante el calentamiento global del siglo XX (desde ~1900) y 2) incremento en las actividades antrópicas (con mayor evidencia en la región pampeana) combinadas con las características propias y locales de cada ambiente (régimen hídrico, cuenca, procesos intrínsecos). The paleoenvironmental and paleoclimatic reconstructions based on proxies from lake sediments provide information about the dynamic of lakes and the responses of these ecosystems to past climatic variability, at different time scales from millennia to decades. Changes in climate and anthropogenic activities are the main drivers of changes in aquatic ecosystems. Subfossil chironomids (Diptera: Chironomidae) are useful paleoindicators due to their specific response to past environmental conditions. In addition, they can be used in multiproxy studies as an independent information of past environmental conditions. Last paleoclimate records from northern of Patagonia and central of Argentina indicated a regional contrast related to precipitations and temperature along the so call “Diagonal Arida” Argentina. This narrow climatic band distinguishes twogroups of lakes systems with different hydrological regime and with diverse paleohydrological responses to short climatic phases such as the Little Ice Age. The aim of this Thesis was to study the environmental variations (natural and anthropic) recorded during the last ca. 1000 years on both sides of the “Diagonal Arida” (DA) in order to provide new evidences of the asynchronous regional climate (anti-phase). To meet the objectives, chironomid assemblages from lakesla Barrancosa (37 °S), southwest of the province of Buenos Aires (Pampean region) and from lakesVerde and Toncek) (41 °S) in northwestern Patagonia were analyzed and compared to reconstruct the environmental history of each lake and the dominant climatic phases during the last 1000 years. Complementary information fromgeochemical parameters such as fossil pigments (CD, TC), organic matter and, when it was available, nutrients and ostracods were used to reconstruct the paleolimnological conditions of the each lake. Results from the multiproxy analysis from each sedimentary sequence, allowed to detect different periods associated each one to different environmental conditions.Three climatic periods were defined on thepaleoenvironmental history of lake La Barrancosa. The first period,between ~610-1278 AD, dry/ wet climatic fluctuations were inferred. The last part of this period was associated to the Warm Medieval Anomaly. The second period, between ~1278-1947 AD, a negative hydrological balance was detected which was associated to the Little Ice Age. Finally, the third period, between 1947-2012 AD, wet climatic conditions were inferred associated to the increase of regional precipitation since 1940 ca. The environmental dynamics oflakeLa Barrancosa reveals a hydroclimatic variability and human impact trends in the area during the 20th century. During the 15th century, the Barrancosa sedimentary record allowed to infer negative hydrological balance and theestablishment of a temporary, sub-saline environment. An ecological regional shiftat the 1970s marks the onset of the mid-20th century climatic amelioration driven by changes in circulation patterns and precipitations, allowed the establishment of a clear waters shallow lake. Since 1990, the eutrophication processes were accelerated, probably as a consequence of the great increase in the agriculture around the lake and the transition from the traditional to modern techniques based on extensive use of fertilizers and pesticides in the region. Other activities such as the introduction of the fish species Odontesthes bonariensis, could have favoured eutrophication processes in this lake.The subfossil chironomid records from lakes Verde and Toncek documented changes in the assemblage composition and absolute abundance in the last ca. 500 yrs in response to a combination of diverse environmental drivers.Three climatic periods were defined in the paleoenvironmental history of lake Verde. The first period, between 1561-~1670 AD was dominated by cold and wet climatic conditions and associated, in part, with the Little Ice Age; a second period, between ~1670-~1878 AD, was dominated dry climatic conditions mainly in the last part of the period and, a third period, between ~1878-2012 AD, dominated by warm climatic conditions associated with the current global warmingperiod. The paleolimnological record of lake Toncek was divided in two climatic periods. The first period, between ~1644-1960 AD, was dominated mostly by cold conditions coincident with Little Ice Age, a second period, between 1960 AD and 2012 AD, was synchronous to the current general trend of increasing temperatures associated with current global warmingperiod. These climatic conditions allowed more productive conditions. Ash falls from nearby volcanoes appear to be one of the factors of change in the chironomid assemblages mainly in lake Toncek although in the last ca. 50 years, climate warming and human impacts have also been responsible for changes in the midge communities of each lake. Superimposed to volcanism, others environmental factors interplay in the lake ecosystem, such as hydrology, watershed characteristics and quality and quantity of organic matter as key to understanding changes in the composition and diversity of biota in remote lakes through time.Summarizing, the paleocommunities of chironomids of each environment studied reflected important changes in its composition and abundance related to climatic, hydrological and anthropic drivers acting during the last 1000 years in the southwest of the province of Buenos Airesand, in the last 500 years in the northwest of Patagonia although the most important changes, in the last two lakes were evident in the last 100 years. During the last 200 years, the impact of volcanic tephra from nearby Chilean volcanoes caused importantchange to the chironomid records from the northern patagonian lakes. The paleoenvironmental reconstructions from the studied lakes allowed to detect different response patterns in terms of water level changes, climate and productivity changes at both sides of the “Diagonal Arida” especially during the so called LIA. Hydroclimatic changes during the last 1000 years were more evident in the Pampas lake, La Barrancosa. On the other hand, in all the records, productivity changes were observed in the last 100 years which could be linked to 1) general trend of increasing temperatures observed in South America since 1900AD and 2) to anthropic drivers (mainly at lake La Barrancosa) combined with local environmental characteristics such as hydrology, catchment area,intrinsec process, between others. Fil: Montes de Oca, Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Administración de Parques Nacionales. Delegación Regional Patagonia; Argentina