A new species of Stethelmis Hinton (Coleoptera: Elmidae) from Argentina and description of its larva.

A new species of Stethelmis, S. shepardi sp. nov., is described for Patagonia, Argentina from adults of both sexes. A full description and illustrations of both the adult and the larva of the new species are provided with comments on its habitat and distribution. Adults of the new species are compared with those of S. kaszabi (Hinton 1970) and S. chilensis (Hinton 1945). The larva of S. shepardi is compared with that of S. kaszabi, the other Stethelmis larva described. We also describe and illustrate for the first time the male genitalia of S. kaszabi. A key to the known species of Stethelmis is also included.

Description of immatures of Berosus decolor Knisch, 1924 (Coleoptera: Hydrophilidae: Berosini), with emphasis on chaetotaxy and morphometry.

The preimaginal stages of Berosus decolor Knisch, 1924 are described for the first time, including illustrations of the egg case and all larval instars. Larval morphology of this species is studied emphasizing chaetotaxic and morphometric analyses. The egg case lacks a mast and contains 2‒3 eggs; all larval instars are characterized by the following features: presence of 6 teeth on anterior margin of nasale; left epistomal lobe carrying 14‒16 strong and curved setae (gFR2); seta FR1 elongate, inserted posteriorly to seta PA7; pore FR14 absent; parietale with spinulae in the area between setae PA5 and PA12; mandibles asymmetrical; seta MN1 minute; first antenommere with a digitiform projection on distal inner margin; antennal sensilla AN8 and AN9 absent; maxillary sensilla MX10 hair-like, MX11 and MX16 with an intermediate shape between hair-like and spine-like; labial sensilla LA4 and LA15 absent; seta LA2 present, minute; abdomen with 7 pairs of tracheal gills. The morphology of the egg cases and larvae within the genus Berosus are compared and discussed.

A new species of Luchoelmis Spangler & Staines (Coleoptera: Elmidae) from Argentina and its probable larva.

A new species of riffle beetle from southwestern Argentina, Luchoelmis kapenkemkensis, is described. Its diagnostic characters are illustrated and the key for the identification the species of the genus is updated. A larva, very likely belonging to this species, is also described and compared to other related larvae.

Description of immatures of the genus Tropisternus Solier, subgenus Pristoternus Orchymont (Coleoptera: Hydrophilidae), with emphasis on the chaetotaxy and morphometry of larval forms.

The egg cases, larvae, and pupae of Tropisternus (Pristoternus) latus (Brullé, 1837), T. (P.) ovalis Castelnau, 1840, and T. (P.) laevis (Sturm, 1826) are illustrated and described for the first time. The egg cases are built with or without a mast, which can be ribbon-like or globular; all larval instars have seven anterior denticles in the anterior margin of nasale, and the antennal seta AN8 is present; the pupae bear 6 or 8 styli on the abdominal segments II-VI, the pleural styli can be either short or very long, and horn-like projections may be present on the abdominal segments II-VI. A comparison of the morphology of the egg cases, pupae and larval chaetotaxic and morphometric characters within the genus Tropisternus is presented.

Larval chaetotaxy and morphometry of Megasternini: Cercyon (Paracercyon) Seidlitz, Cryptopleurum Mulsant and Pelosoma Mulsant (Coleoptera: Hydrophilidae).

The chaetotaxy of the head capsule and head appendages of all the larval instars of Cercyon (Paracercyon) analis and the first and third instars of Cryptopleurum minutum and Pelosoma sp. is described and illustrated for the first time. Morphometric characters derived from the head capsule and mouthparts are also included, together with detailed illustrations of all characters. The morphology and chaetotaxy of these larvae are compared to that of other Megasternini with described larvae. The larval morphology of Megasternini has proven to be very similar, however we provided a group of chaetotaxic characters useful to separate genera. Most of the differences were found in the sensilla of the head capsule, maxilla, and labium, both in size and arrangement, while the chaetotaxy of the antennae and mandibles was strongly conserved.

Beetle mania: Understanding pond aquatic beetles diversity patterns through a multiple-facet approach.

Ecological studies searching for drivers of biodiversity variation have frequently focused on taxonomic richness. However, more aspects of biodiversity, namely diversity facets can be considered to properly assess biotic-environment relationships. Here, we explore the environmental factors that could control the four biodiversity facets of aquatic Coleoptera from 93 regionally sampled Patagonian ponds. We also explore which are the ponds with high diversity values of all facets to prioritize them with a high conservation value. We fitted generalized additive models (GAM) to test relationships among environment (i.e., local and climatic variables) and aquatic beetles diversity facets (i.e., richness (SD), functional diversity (FD), phylogenetic diversity (PD), and local contribution to local beta diversity (LCBD). Climatic drivers were the most important predictors of beetle diversity facets, which exhibited linear and nonlinear responses. Thus, ponds from warmer Patagonia exhibited the highest values of SD and PD, whereas LCBD also peaked on colder sites suggesting that ponds under extreme temperatures sustain unique beetle assemblages. Moreover, ponds located in areas with higher precipitation variability exhibit the highest values of LCBD (i.e., unique assemblages). This result in addition to arid conditions in Patagonia prevailing since 16 m.y.a made us think that Patagonian beetle pond-dwellers are basally adapted to aridity. We calculated an index that summarizes the four facets patterns, to assign high conservation value to those ponds with higher index values. The relative importance of each facet varies from pond to pond. Hence, this multifaceteded approach not only allows us to identify priority areas for biodiversity conservation but also focuses on the importance of including multiple facets to understand biodiversity spatial patterns.

Chaetotaxy and morphometry of the head capsule and head appendages of the genus Derallus Sharp (Coleoptera: Hydrophilidae).

The primary and secondary chaetotaxy of the head capsule and head appendages of the three larval instars of the water scavenger beetle genus Derallus Sharp are described for the first time based on two species: D. angustus Sharp and D. paranensis Oliva. Morphometric characters derived from the head capsule and mouthparts are included, together with detailed illustrations of all characters. Chaetotaxy of these larvae is compared with that of Regimbartia attenuata (Fabricius), another species belonging to the Derallus-clade of Berosini.

Description of the putative mature larva of the Neotropical genus Stenhelmoides Grouvelle (Coleoptera: Elmidae).

Stenhelmoides Grouvelle is a Neotropical genus of Elmidae and although it exhibits a wide distribution, until now no larvae had been associated with adults of this genus. Larvae, very likely belonging to this genus, were associated based on co-occurrence with adults. Eleven larvae and nine adults were examined from ten localities at altitudes between 30 and 682 m a.s.l. in the Andean, Caribbean and Pacific regions in Colombia. Mature larvae of the Stenhelmoides rufulus (Hinton) are described and illustrated for the first time. A larval diagnosis for the genus is presented; body shape, distribution and form of setae and number of pleural sclerites are diagnostic characters for larvae of this genus. Comparative notes with similar larvae of other Elmidae genera are presented. The existing generic keys are updated to include larvae of Stenhelmoides. Comments on distribution and habitat of Stenhelmoides larvae are also provided. This work contributes to enhance the knowledge of Neotropical larvae, which have been described for only approximately 56% of genera and 8% of species of Elmidae.

Biotic diversity of benthic macroinvertebrates at contrasting glacier-fed systems in Patagonia Mountains: The role of environmental heterogeneity facing global warming.

Patagonia is by far the largest glacierized area in South America. However, little is known about ecology, functioning and biodiversity of glacier-fed streams facing global warming. We investigated changes in environmental features and macroinvertebrate communities along a longitudinal gradient of glacier influence of two Patagonian systems that differ in glacier cover magnitude and the spatial sequence of lotic and lentic phases. Both glaciers, Torrecillas (~5.5km2, Torrecillas system) and Cónico (~0.44km2, Baggilt system), are retreating. Longitudinal distribution of benthic invertebrates partially fitted to predictions for glacierized temperate systems, with Diamesinae spp. dominating at closest sites to the Cónico, and Orthocladiinae increasing downstream, but patterns were unclear at Torrecillas. Generalized Linear Model identified chlorophyll a and conductivity as having significant effect on richness and density respectively at Torrecillas; detritus biomass and gravel influenced species richness, and boulder percentage and water temperature affected density, at Baggilt. Canonical Correspondence Analyses integrating benthic biota and environmental variables revealed that a higher environmental heterogeneity at Baggilt, related with spatial dimension (unshaded/shaded reaches, wetland reaches), local resources (detritus, bryophytes) and temperature, probably explained the unexpected high richness in benthic assemblages (67 taxa). Environmental conditions imposed by the lake outlet (proglacial) at Torrecillas resulted in a less diverse community (31 taxa). Finally our results suggest that these isolated, small glacier-fed streams typical of the Patagonian landscape appear highly vulnerable to global warming. Endemic elements could disappear at upper segments being replaced by other species common at rhithral environments, which might increase local diversity (alfa diversity) but decrease regional diversity (gamma diversity). From an ecosystem perspective stream functioning can result altered. Glacier retreating or disappearing threatens major ecosystem services for Patagonian inhabitants such as water supply, hydrological regulation, recreation and tourism.

Description of the mature larva of Austrolimnius nyctelioides (Germain, 1892) and A. elatus Hinton, 1941 (Coleoptera: Elmidae).

Mature larvae of two species of the riffle beetle genus Austrolimnius Carter & Zeck, 1929 are described and illustrated for the first time: Austrolimnius nyctelioides (Germain, 1892) and A. elatus Hinton, 1941. A larval diagnosis for the genus is presented and both larvae are compared with each other and with the previously described larva of A. mucubajiensis Gómez & Bello, 2006. Comments on the species' habitats are included.

Austrelmis Brown (Coleoptera: Byrrhoidea: Elmidae) from Argentina: five new species.

Material belonging to the genus Austrelmis Brown, from different localities from northwestern Argentina, is studied and described. Five new species are described and illustrated from adults of both sexes: Austrelmis argentinensis sp. nov., A. catamarcensis sp. nov., A. talampayensis sp. nov., A. tafi sp. nov. and A. robustus sp.nov. The new species are compared to other known species of the genus. A comparative table summarizing the most important characters used to identify the argentine species of Austrelmis and a distributional map for Argentina are included.

Environmental changes and macroinvertebrate responses in Patagonian streams (Argentina) to ashfall from the Chaitén Volcano (May 2008).

On May 2nd of 2008 the Chaitén Volcano (Chile, 42°50'S and 72°39'W) erupted explosively producing a strong emission of volcanic ash. As a result of this eruption wide areas on the Argentinean side became covered by ashes. In order to investigate the effects of ashfall on environmental features, water quality and macroinvertebrate communities we conducted a study on 10 rivers affected by ash deposition in their hydrographic basins. Sites were visited seasonally (June 2008-March 2010) and results were compared with data obtained from previous research projects. Measures of pH, conductivity, oxygen content, main nutrients, and total suspended solids (TSS) were taken. Macroinvertebrate samples were obtained from riffles and pools. Community attributes were measured and metrics were calculated. A strong and significant increase in TSS values at most sites was recorded and although the peak diminished rapidly during the following months, resuspension and remobilization of ash continue even 20 months after. No significant changes in pH, conductivity and nutrients, comparing with data previous to the ashfall, were detected. Most rivers showed a strong diminution on macroinvertebrate density and richness, being small rivers more severely affected than the big ones. Correspondence analysis based on abundance data allows distinguishing preeruption from posteruption dates at five rivers. Density data and species richness showed low values in March of 2010, indicating that the community was not completely recovered at some sites. At least 25 taxa resulted significantly and negatively affected. Increased mortality could be related to several factors such as habitat deterioration, food quality diminution, interference with breathing mechanisms and with other physiological and morphological characteristics. Specific-taxa responses on the recolonization process were related to dispersal mechanisms and specific strategies.

Assessing land-use effects on water quality, in-stream habitat, riparian ecosystems and biodiversity in Patagonian northwest streams.

Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.