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Species Likely (species + likely)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Forks in the Road: Choices in Procedures for Designing Wildland Linkages

CONSERVATION BIOLOGY, Issue 4 2008
PAUL BEIER
análisis de sensibilidad; conectividad; corredor de vida silvestre; enlace; diseño de reservas Abstract:,Models are commonly used to identify lands that will best maintain the ability of wildlife to move between wildland blocks through matrix lands after the remaining matrix has become incompatible with wildlife movement. We offer a roadmap of 16 choices and assumptions that arise in designing linkages to facilitate movement or gene flow of focal species between 2 or more predefined wildland blocks. We recommend designing linkages to serve multiple (rather than one) focal species likely to serve as a collective umbrella for all native species and ecological processes, explicitly acknowledging untested assumptions, and using uncertainty analysis to illustrate potential effects of model uncertainty. Such uncertainty is best displayed to stakeholders as maps of modeled linkages under different assumptions. We also recommend modeling corridor dwellers (species that require more than one generation to move their genes between wildland blocks) differently from passage species (for which an individual can move between wildland blocks within a few weeks). We identify a problem, which we call the subjective translation problem, that arises because the analyst must subjectively decide how to translate measurements of resource selection into resistance. This problem can be overcome by estimating resistance from observations of animal movement, genetic distances, or interpatch movements. There is room for substantial improvement in the procedures used to design linkages robust to climate change and in tools that allow stakeholders to compare an optimal linkage design to alternative designs that minimize costs or achieve other conservation goals. Resumen:,Los modelos son utilizados comúnmente para identificar tierras que mantengan la habilidad de la vida silvestre para moverse entre bloques de tierras silvestres a través de una matriz de tierras que habían sido incompatibles con el movimiento de vida silvestre. Ofrecemos 16 opciones y supuestos que se originan en el diseño de enlaces para facilitar el movimiento o el flujo de genes de especies focales entre 2 o más bloques de tierras silvestres predefinidos. Recomendamos el diseño de enlaces que sirvan a múltiples (y solo a una) especies focales que funjan como una sombrilla colectiva para todas las especies nativas y los procesos ecológicos, que explícitamente admitan supuestos no comprobados y que utilicen análisis de incertidumbre para ilustrar efectos potenciales de la incertidumbre del modelo. La mejor forma de mostrar tal incertidumbre a los interesados es mediante mapas de los enlaces modelados bajo diferentes suposiciones. También recomendamos modelar a habitantes de corredores (especies que requieren más de una generación para mover sus genes entre bloques de tierra silvestre) de manera diferente que las especies pasajeras (un individuo se puede mover entre bloques de tierras silvestres en unas cuantas semanas). Identificamos un problema, que denominamos el problema de traducción subjetiva, que surge porque un analista debe decidir subjetivamente cómo traducir medidas de selección de recursos a resistencia. Este problema puede ser sobrepuesto mediante la estimación de la resistencia a partir de observaciones de movimientos de animales, distancias genéticas o movimientos entre fragmentos. Hay espacio para la mejora sustancial de los procedimientos utilizados para diseñar enlaces robustos ante el cambio climático y en herramientas que permiten que los interesados comparen un diseño óptimo con diseños alternativos que minimicen costos o alcancen otras metas de conservación. [source]

Species in the genus Turritopsis (Cnidaria, Hydrozoa): a molecular evaluation

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2007
M. P. Miglietta
Abstract Mitochondrial ribosomal gene sequences were used to investigate the status of several populations of hydromedusae belonging to the genus Turritopsis (family Oceaniidae). Several nominal species have been described for this genus, but most of them had been synonymized and attributed to one cosmopolitan species, Turritopsis nutricula. A recent revision based on morphological and reproductive characters, however, has shown that many different populations can be distinguished and that several of the nominal Turritopsis species are likely valid biological species. Our investigation using molecular sequence data of 16S mitochondrial gene confirms these results. The Mediterranean Turritopsis must be attributed to Turritopsis dohrnii and the Turritopsis of New Zealand must be referred to Turritopsis rubra. The situation of the Japanese Turritopsis is more complex, though all sampled populations are clearly distinct from T. nutricula, a species likely confined to the Western Atlantic. The Japanese Turritopsis fall into three widely separated lineages. One of them, corresponding likely to Turritopsis pacifica, is closely related to T. rubra. A second clade, which potentially represents an as yet undescribed species, produces smaller medusae than T. pacifica and is morphologically distinguishable from it. Finally, a third group was distinguished by a single haplotype sequence that is identical with a Mediterranean sample of T. dohrnii. It is postulated that the last group of Japanese Turritopsis is likely a recent introduction, most probably by human activity. A survey of all known and potentially valid Turritopsis species is given in table format to facilitate identifications and future revisory work. Sommario Sequenze del gene mitocondriale 16S sono state utilizzate per studiare lo stato tassonomico di idroidi appartenenti al genere Turritopsis (Famiglia Oceaniidae). In letteratura, tra le numerose specie nominali di TurritoSPSis descritte, molte di queste sono state successivamente messe in sinonimia e attribuite ad un'unica specie cosmopolita, Turritopsis nutricula. Una recente revisione, basata su dati morfologici e caratteri riproduttivi, ha comunque mostrato che diverse popolazioni di Turritopsis possono essere distinte in numerose specie nominali e probabilmente rappresentano valide specie biologiche. Il presente studio conferma questa recente interpretazione, mediante lo studio di sequenze molecolari del gene 16S. La popolazione mediterranea di Turritopsisè ora attribuita a T. dohrnii, mentre la popolazione neozelandese va ascritta alla specie T. rubra. La situazione nei mari giapponesi si presenta piu' complessa, sebbene tutte le popolazioni ivi campionate siano chiaramente distinte da T. nutricula, la quale risulta confinata unicamente all'Atlantico Orientale. Le sequenze ottenute da esemplari di Turritopsis provenienti dal Giappone formano tre cladi ben distinti. Uno di essi corrisponde a Turritopsis pacifica. Un secondo clade è costituito da popolazioni che producono meduse piu' piccole rispetto a Turritopsis pacifica ed e' dunque anche morfologicamente separato. Un terzo gruppo e' rappresentato da un solo aplotipo identico alle popolazioni mediterranee di T. dohrnii. La presenza di quest'ultimo gruppo di Turritopsis in Giappone e' molto probabilmente il risultato di un'introduzione recente, in seguito ad attività umana. Per facilitare futuri lavori di revisione, è inoltre presentata tavola che riassume le caratteristiche di tutte le specie di Turritopsis conosciute e potenzialmente valide. La tavola cerca di integrare i dati morfologici e riproduttivi già noti e dei dati molecolari ottenuti con questo studio. [source]

Spatial distributions of multiple plant species affect herbivore foraging selectivity

OIKOS, Issue 2 2010
Ling Wang
Spatial distribution of food resources is an important factor determining herbivore foraging. Previous studies have demonstrated that clumped distribution of preferred species increases its consumption by herbivores in single- or two-species systems. However, the potential impact of distribution pattern of less preferred species on foraging was ignored. In natural grasslands with high species diversity and complexity, the spatial distribution of preferred species impacts on herbivore foraging may be strongly correlated with the distribution of less preferred species. Our aims were to determine the effect of distribution of both preferred and other plant species on herbivore foraging under conditions close to a native, multi-species foraging environment, and conceptualize the relationships between spatial distribution of food resources and herbivore consumption. We hypothesized that random distribution of non-preferred species reduces herbivore consumption of preferred species because the dispersion of less preferred species likely disturbs herbivore foraging. We conducted an experiment using three species with five combinations of clumped and random distribution patterns. Three species Lathyrus quinquenervius, Phragmites australis and Leymus chinensis, were of high, intermediate and low preferences by sheep, respectively. Results showed that distribution of low preferred species, but not that of high preferred one, affected the consumption of preferred species. Sheep obtained higher consumption of high preferred species when low preferred species followed a clumped distribution than a random distribution. Distance between aggregations of high and low preferred species did not affect sheep foraging. It was concluded that the effects of spatial distribution of preferred species on its consumption are dependent on herbivore foraging strategy, and sheep can consume more preferred species when there is a consistent spatial pattern between preferred species and the entire food resource, and that the random dispersion of low preferred species in grassland may reduce herbivore consumption of high preferred species, thus minimizing selective grazing. [source]

Endangered, apparently: the role of apparent competition in endangered species conservation

ANIMAL CONSERVATION, Issue 4 2010
N. J. DeCesare
Abstract Conservation biologists have reported growing evidence of food-web interactions as causes of species endangerment. Apparent competition is an indirect interaction among prey species mediated by a shared predator, and has been increasingly linked to declines of prey species across taxa. We review theoretical and empirical studies of apparent competition, with specific attention to the mechanisms of asymmetry among apparently competing prey species. Asymmetry is theoretically driven by niche overlap, species fitness traits, spatial heterogeneity and generalist predator behavior. In real-world systems, human-induced changes to ecosystems such as habitat alteration and introduced species may be ultimate sources of species endangerment. However, apparent competition is shown to be a proximate mechanism when resultant changes introduce or subsidize abundant primary prey for predator populations. Demonstration of apparent competition is difficult due to the indirect relationships between prey and predator species and the potential for concurrent exploitative competition or other community effects. However, general conclusions are drawn concerning the characteristics of prey and predator species likely to exhibit asymmetric apparent competition, and the options for recovering endangered species. While short-term management may be required to avoid imminent extinction in systems demonstrating apparent competition, we propose adaptive conservation efforts directed at long-term recovery. [source]