Description of immature stages of Agelanius cortesi (González) from central Chile (Diptera: Tabanidae)

The immature stages of Agelanius cortesi are described and illustrated from immatures collected in Quebrada Los Almendros, Río Clarillo National Reserve, Cordillera Province, central Chile, and reared in the laboratory. Larvae of A. cortesi were found below the soil surface associated with other invertebrates.

Resumen

Se describe e ilustra los estados inmaduros de Agelanius cortesi colectados en la Quebrada Los Almendros, Reserva Nacional Río Clarillo, Provincia Cordillera de Chile central, los cuales fueron criados en el laboratorio. Las larvas de A. cortesi fueron encontradas bajo la superficie del suelo asociadas con otros invertebrados.     

Molecular Evidence for Multiple Origins of Hybridogenetic Fish Clones (Poeciliidae: Poeciliopsis)

Hybrid matings between the sexual species Poeciliopsis monacha and Poeciliopsis lucida produced a series of diploid all-female lineages of P. monacha-lucida that inhabit the Río Fuerte of northwestern Mexico. Restriction site analyses of mitochondrial DNA (mtDNA) clearly revealed that P. monacha was the maternal ancestor of these hybrids. The high level of mtDNA diversity in P. monacha was mirrored by similarly high levels in P. monacha-lucida; thus hybridizations giving rise to unisexual lineages have occurred many times. However, mtDNA variability among P. monacha-lucida lineages revealed a geographical component. Apparently the opportunity for the establishment of unisexual lineages varies among tributaries of the Río Fuerte. We hypothesize that a dynamic complex of sexual and clonal fishes appear to participate in a feedback process that maintains genetic diversity in both the sexual and asexual components.     

A new species of Acestrocephalus (Characiformes: Characidae) from Venezuela

A new species of Acestrocephalus is described from 60 specimens collected in the Río Orinoco and Río Negro drainages, Venezuela. This species is distinguished from all other Acestrocephalus by the combination of the following characters: anal rays, 29-36; 63-71 perforated scales on the lateral line; 10-12 scales above and 9-12 below the lateral line; 39-52 teeth on the maxillary; 9-12 premaxillary teeth; 8-12 teeth in the inner row on the dentary; 5-7 gill rakers on the lower part of the first gill arch; humeral, peduncular and caudal blotch absent.     

Geographic distribution and demography of Pithecia aequatorialis (pitheciidae) in Peruvian Amazonia

To study the geographic distribution and demographic characteristics of Pithecia aequatorialis in Peruvian Amazonia, we undertook surveys and transect census in three river basins (Río Itaya, Río Tigre and Río Curaray) between 2004 and 2008. A total of 123 groups of P. aequatorialis was encountered during 1623 km of transect walks. Group size was uniform among the three areas (3.4–3.6 individuals), but surprisingly, population densities were higher in the area with strong hunting pressure (Río Itaya: 7.8 ind./km², vs. 5.6 and 5.9 km² in the Río Tigre and Río Curaray basins, respectively). The most common group composition included an adult pair with one offspring. Groups with more than one adult male and/or female accounted for 35% of sightings. Our observations extend P. aequatorialis range in Peru further south to the area between the Río Tigre and Río Corrientes, but exclude the area to the north between the Río Curaray and Río Napo. These findings are in contrast to previous distribution maps. P. aequatorialis was rarely seen in interspecific association during our censuses. Am. J. Primatol. 71:964–968, 2009. © 2009 Wiley‐Liss, Inc.     

Fish assemblage of a Pampasic stream (Buenos Aires,Argentina): temporal variations and relationships with environmental variables

In the Argentine Pampa fertile soils were originally covered by grasslands, but at present are intensively cultivated. We assessed the specific composition of the fish assemblage of El Pescado stream and compared it with that recorded in 1991–1993, when land use in the watershed consisted in natural pastures. The persistence of the fish assemblage between the two studies was rather high: 0.76. Abundance, biomass and species richness were higher during drought periods. Connectivity with the huge Río de la Plata hydrographic system seems the most important contribution to the high and stable species richness of El Pescado stream.     

New Middle Miocene Caviomorph Rodents from Quebrada Honda,Bolivia

The rodents of the middle Miocene fauna of Quebrada Honda Bolivia are described. The most abundant rodent is the chinchillid Prolagostomus sp. More precise identification of this species will require revision of early to middle Miocene lagostomines, taking into account variation in modern populations. The next most common rodents are the tiny octodontoid Acarechimys, sp. nov.?, and the caviid Guiomys unica. The Acarechimys species may be unique to Quebrada Honda, but verification awaits revision of this geographically and temporally widespread genus. Guiomys unica is a recently described species otherwise known only from two Patagonian localities, El Petiso and Río Chico. Two rodents are unique to Quebrada Honda. Mesoprocta hypsodus, gen. et sp. nov., is a dasyproctid distinguished by its very hypsodont, cement-covered cheek teeth. Quebradahondomys potosiensis, gen. et sp. nov., is an adelphomyine echimyid distinguished by the less oblique lophids of its trilophodont cheek teeth, among other features. The rodents of Quebrada Honda are more similar to those of Patagonia than those of northern South America, paralleling patterns seen in other mammal groups from this fauna.     

Paleofloristic assemblage from the Paleogene Río Guillermo Formation,Argentina: preliminary results of phylogenetic relationships of Nothofagus in South America

Hünicken's paleobotanical collection is one of the most important in South America because it was the first one to be related to a documented stratigraphic profile. This floristic assemblage (Oligocene) recovered from Río Guillermo Formation, at Estancia Tres Marías, Río Guillermo Valley, Santa Cruz, Argentina, is described by the first time in this paper. Five species of genus Nothofagus (N. subferruginea, N. serrulata, N. crenulata, N. elongata and N. variabilis) together with Myrcia bagualense are components of the assemblage. The presence of Acaena brandmayri is confirmed for the first time for the area. Paleoenviromental and paleoclimate implications are also discussed. Characteristic species from a temperate-cold climate such as the genus Nothofagus are present in the material studied. A phylogenetic study of the fossil species herein described and the extant South American species of Nothofagus is presented. The preliminary results support the hypothesis that fossil species of Nothogafus are closely related to the modern species.     

Epilithic Algae Distribution Along a Chemical Gradient in a Naturally Acidic River, Río Agrio (Patagonia, Argentina)

The epilithic algae distribution along a pH gradient and the relationship between the chemical gradient and biomass development were studied in Río Agrio, a naturally acidic river located in Patagonia (Argentina). The epilithic community was monitored during the summer of three consecutive years in sites located above and below the entrance of tributaries. The epilithic community showed differences between sites based on the chemical composition of the water and the precipitates that appear on the streambed of the river. The lowest biomass, diversity, and number of species were found at the most extreme part of the river in terms of pH (ca. 2) and element concentrations. Euglena mutabilis was the dominant species in this section of the river. As pH increased (ca. 3), the community changed to be dominated by filamentous green algae (Ulothrix spp., Mougeotia sp., Klebsormidium sp.) showing luxuriant growths in terms of biomass. With the inflow of a neutral tributary, the pH of Río Agrio increased above 3, and the precipitates of orange-red iron hydroxides appeared. The algal community was not affected by these precipitates or the low P concentrations, along the next 30 km of river downstream from this site. The apparent physical stress that the precipitates impose on algae is in fact a dynamic reservoir of P because diel cycle of Fe could be promoting precipitation and redissolution processes that binds and releases P from these precipitates. Where the pH increased above 6, precipitates of aluminum hydroxides appeared. At this site, the epilithic biomass and density decreased, some algae species changed, but the diversity and the number of species in general remained consistent with the upstream values. The physical stress of the Al precipitates on the algae is added to the chemical stress that represents the sequestering of P in these precipitates that are not redissolved, resulting P a limiting nutrient for algae growth.     

Species delimitation in a range-restricted group of cascudinhos (Loricariidae: Epactionotus) supports morphological and genetic differentiation across coastal rivers of southern Brazil

Epactionotus species are known for inhabiting the rocky-bottom stretches of fast-flowing rivers in a limited geographic area along the Atlantic coast of southern Brazil. These species are endemic to single coastal river drainages (two neighbouring drainages for Epactionotus bilineatus) isolated from each other by the coastal lacustrine environments or the Atlantic Ocean. E. bilineatus is from the Maquiné and Três Forquilhas River basins, both tributaries of the Tramandaí River system, whereas E. itaimbezinho is endemic to the Mampituba River drainage and Epactionotus gracilis to the Araranguá River drainage. Recent fieldwork in the Atlantic coastal drainages of southern Brazil revealed new populations in the Urussanga, Tubarão, d'Una and Biguaçu River drainages. Iterative species delimitation using molecular data (cytochrome c oxidase subunit I) and morphology (morphometrics and meristics) was applied to evaluate species recognition of isolated populations. With regard to new data, the genus was re-diagnosed, the status of Epactionotus species/populations was re-evaluated, formerly described species were supported and population structure was recognized. As for the newly discovered populations, both morphological and molecular data strongly support the population from the Biguaçu River drainage, in Santa Catarina State, as a new species. Molecular data revealed strong per-basin population structure, which may be related to species habitat specificity and low or no dispersal among drainages.     

Pinus georginae (Pinaceae), a new species from western Jalisco, Mexico

Pinus georginae is described and illustrated as a new endemic species from the valleys in the southern basin of Río Ameca, Jalisco, western Mexico. It is closely related to Pinus praetermissa; however, after studying the cones and anatomy of the leaves in detail, characteristics were revealed that identify P. georginae as a distinct species.

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Resumen  Se describe e ilustra Pinus georginae como una especie nueva, endémica de algunos valles intermontanos al sur del Río Ameca, Jalisco, en el Occidente de México. Los árboles se parecen a Pinus praetermissa; sin embargo, al estudiar con detalle los conos y la anatomía de las acículas lo ubican a Pinus georginae como una entidad biológica con categoría específica independiente.

     

Eukaryotic community distribution and its relationship to water physicochemical parameters in an extreme acidic environment, Rio Tinto (southwestern Spain)

The correlation between water physicochemical parameters and eukaryotic benthic composition was examined in Río Tinto. Principal component analysis showed a high inverse relationship between pH and most of the heavy metals analyzed as well as Dunaliella sp., while Chlamydomonas sp. abundance was positively related. Zn, Cu, and Ni clustered together and showed a strong inverse correlation with the diversity coefficient and most of the species analyzed. These eukaryotic communities seem to be more influenced by the presence of heavy metals than by the pH.     

A new species of Profundulus (Cyprinodontiformes: Profundulidae) from the Honduran central highlands

A new species of Profundulus, Profundulus portillorum, from the Honduran central highlands is described. Profundulus portillorum belongs to the Profundulus labialis species group and is distinct from the Profundulus punctatus species group in that it lacks a humeral spot and less than half of the caudal fin is scaled. Within the P. labialis species group, P. portillorum has a more slender body, smaller eye, fewer anal rays, caudal rays and lateral‐line scales than other species. Forty‐one specimens were collected around emergent vegetation in the margins of two small (2–5 m in width, 20–40 cm in depth), high‐elevation (1300 m) tributaries of the Río Calam within the Río Ulúa drainage. These specimens represent the easternmost collection of any Profundulus and the first collection of any member of the P. labialis species group from Honduras.     

Three new legumes endemic to the Marañón Valley,Perú

Two new species of legume, Caesalpinia celendiniana and Mimosa lamolina and one new variety, Caesalpinia pluviosa var. maraniona, from the inter-Andean Río Mara?ón Valley in northern Perú are described and illustrated. These add to the already impressive tally of endemics known from the seasonally dry tropical forests of the Río Mara?ón Valley, which apparently far exceeds the endemic plant diversity from other nearby inter-Andean dry valleys in Perú and southern Ecuador.     

A new species of Jaltomata (Solanaceae) from northwestern Peru

Jaltomata whalenii, a rare species endemic to the Río San Benito drainage in the department of Cajamarca, Perú, is described and illustrated. The delimitation and relationships of the genusJaltomata are briefly discussed.     

Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

The Pacific Arctic marine ecosystem has undergone rapid changes in recent years due to ocean warming, sea ice loss, and increased northward transport of Pacific-origin waters into the Arctic. These climate-mediated changes have been linked to range shifts of juvenile and adult subarctic (boreal) and Arctic fish populations, though it is unclear whether distributional changes are also occurring during the early life stages. We analyzed larval fish abundance and distribution data sampled in late summer from 2010 to 2019 in two interconnected Pacific Arctic ecosystems: the northern Bering Sea and Chukchi Sea, to determine whether recent warming and loss of sea ice has restricted habitat for Arctic species and altered larval fish assemblage composition from Arctic- to boreal-associated taxa. Multivariate analyses revealed the presence of three distinct multi-species assemblages across all years: (1) a boreal assemblage dominated by yellowfin sole (Limanda aspera), capelin (Mallotus catervarius), and walleye pollock (Gadus chalcogrammus); (2) an Arctic assemblage composed of Arctic cod (Boreogadus saida) and other common Arctic species; and (3) a mixed assemblage composed of the dominant species from the other two assemblages. We found that the wind- and current-driven northward advection of warmer, subarctic waters and the unprecedented low-ice conditions observed in the northern Bering and Chukchi seas beginning in 2017 and persisting into 2018 and 2019 have precipitated community-wide shifts, with the boreal larval fish assemblage expanding northward and offshore and the Arctic assemblage retreating poleward. We conclude that Arctic warming is most significantly driving changes in abundance at the leading and trailing edges of the Chukchi Sea larval fish community as boreal species increase in abundance and Arctic species decline. Our analyses document how quickly larval fish assemblages respond to environmental change and reveal that the impacts of Arctic borealization on fish community composition spans multiple life stages over large spatial scales.     

A new species of Caesalpinia from the Río Balsas Depression, Mexico, and an updated taxonomic circumscription of the Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae: Caesalpinieae: Poincianella Group)

Caesalpinia oyamae, a new species from the Río Balsas Depression, Mexico, is described and illustrated based on morphological evidence. It is similar toCaesalpinia hintonii, and grows in seasonally dry forests, between 500–1490 m.     

Environmental modulation of reproductive activity of the invasive mussel Limnoperna fortunei: implications for antifouling strategies

Limnoperna fortunei (Dunker, 1857) (Bivalvia) invaded Argentina through the Río de la Plata estuary around 1990 and is presently established throughout five South American countries as a dominant component of the benthic fauna and a major nuisance for industry and power plants. Between 1997 and 2006 we monitored the reproductive activity of L. fortunei through weekly measurements of planktonic larvae in six South American water bodies: Río de la Plata estuary, Paraná and Carapachay rivers, Salto Grande, Itaipú and Embalse de Río Tercero reservoirs. Mean larval densities varied between 4000 and 7000 individuals m^?3; except in the reservoirs of Itaipú (450 ind. m^?3) and Salto Grande (869 ind. m^?3), where the mussel was first recorded shortly before our surveys, and upstream dispersal is limited (Salto Grande). In all cases, reproductive output decreases during the winter. At four of the six sites surveyed larval densities were comparatively high for 8.8–10.2 months per year. A lower food supply is possibly responsible for the shorter reproductive period of 5.9 months at Embalse. At Salto Grande, there is a well‐defined mid‐summer drop in larval numbers, coinciding with blooms of cyanobacteria. We propose that, in addition to temperature, two major factors may regulate the reproductive activity of L. fortunei: (i) the availability of food; and (ii) blooms of toxic cyanobacteria, significantly shortening the otherwise very long reproductive period. This information is important for the design of antifouling programmes involving the use of molluscicides, and has potential for reduced biocide use. These results provide supporting evidence for some fundamental ecological theories of invasions discussed here.     

The relationship between marine fronts and fish diversity in the Patagonian Shelf Large Marine Ecosystem

Aim To evaluate the relationship between marine fronts and (1) fish diversity patterns, (2) fish biomass distribution, and (3) fish assemblage structure. Location Patagonian Shelf, Southwestern Atlantic Ocean. Methods Three main frontal systems and eight nearby zones (frontal vs. non‐frontal areas) were compared. An extensive fishery database, obtained during an a priori sampling scheme (spatial resolution 1 × 1) from 1978 to 1979, was employed. Analyses of 248 trawling stations were performed using a combination of diversity measures (species richness, Shannon diversity and evenness), biomass analyses and multivariate analyses [nonparametric analysis of similarity (ANOSIM), non‐metric multidimensional scaling ordination (NMDS) and similarity percentages (SIMPER)] to evaluate the effect of fronts on fish communities. Results In total, 46 fish taxa were identified. Demersal fish diversity increased at the tidal front of Península Valdés but decreased in the frontal zones of the Southern Shelf‐Break and Magellan frontal systems. The richness and biomass of pelagic fish were higher at the Península Valdés Tidal Front, while the biomass of demersal fish was higher at its non‐frontal counterpart. Fish diversity did not differ consistently along the Northern Shelf‐Break Front. However, a higher fish biomass was registered at the non‐frontal zone. Demersal and pelagic fish assemblages differed between frontal and non‐frontal zones. Main conclusions The Patagonian Shelf Large Marine Ecosystem has diverse frontal types that appear to have different effects on fish diversity and assemblage structure. Seasonal (tidal) or permanent fronts have different effects on the parameters analysed, which could be due to productivity–diversity relationships. The Península Valdés Tidal Front, a relatively short temporal scale system, demonstrates a stronger influence on fish diversity, biomass and assemblage structure than the other frontal areas studied. The seasonality of nutrient input owing to frontogenesis, which begins during the austral spring, may play an important role in determining local diversity. At permanent frontal features, diversity decreases when the nutrient availability is high. This is potentially because, when food resources increase, a few species become dominant.