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Faunal Diversity (faunal + diversity)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Influence of Temporal Scale of Sampling on Detection of Relationships between Invasive Plants and the Diversity Patterns of Plants and Butterflies

CONSERVATION BIOLOGY, Issue 6 2004
RALPH MAC NALLY
But monitoring is often neglected because it can be expensive and time-consuming. Accordingly, it is valuable to determine whether the temporal extent of sampling alters the validity of inferences about the response of diversity measures to environmental variables affected by restoration actions. Non-native species alter ecosystems in undesirable ways, frequently homogenizing flora and fauna and extirpating local populations of native species. In the Mojave Desert, invasion of salt-cedar (Tamarix ramosissima Ledeb.) and human efforts to eradicate salt-cedar have altered vegetation structure, vegetation composition, and some measures of faunal diversity. We examined whether similar inferences about relationships between plants and butterflies in the Muddy River drainage (Nevada, U.S.A.) could have been obtained by sampling less intensively (fewer visits per site over the same period of time) or less extensively (equal frequency of visits but over a more limited period of time). We also tested whether rank order of butterfly species with respect to occurrence rate (proportion of sites occupied) would be reflected accurately in temporal subsamples. Temporal subsampling did not lead to erroneous inferences about the relative importance of six vegetation-based predictor variables on the species richness of butterflies. Regardless of the temporal scale of sampling, the species composition of butterflies was more similar in sites with similar species composition of plants. The rank order of occurrence of butterfly species in the temporal subsamples was highly correlated with the rank order of species occurrence in the full data set. Thus, similar inferences about associations between vegetation and butterflies and about relative occurrence rates of individual species of butterflies could be obtained by less intensive or extensive temporal sampling. If compromises between temporal intensity and extent of sampling must be made, our results suggest that maximizing temporal extent will better capture variation in biotic interactions and species occurrence. Resumen:,El monitoreo es un componente importante de los esfuerzos de restauración y de manejo adoptivo. Pero el monitoreo a menudo es desatendido porque puede ser costoso y consume tiempo. En consecuencia, es valioso determinar si la extensión temporal del muestreo altera la validez de inferencias sobre la respuesta de medidas de diversidad a variables ambientales afectadas por acciones de restauración. Las especies no nativas alteran a los ecosistemas de manera indeseable, frecuentemente homogenizan la flora y fauna y extirpan poblaciones locales de especies nativas. En el Desierto Mojave, la invasión de Tamarix ramosissima Ledeb. y los esfuerzos humanos para erradicarla han alterado la estructura y composición de la vegetación y algunas medidas de diversidad de fauna. Examinamos si se podían obtener inferencias similares sobre las relaciones entre plantas y mariposas en la cuenca Muddy River (Nevada, E.U.A.) muestreando menos intensivamente (menos visitas por sitio en el mismo período de tiempo) o menos extensivamente (igual frecuencia de visitas pero sobre un período de tiempo más limitado). También probamos si el orden jerárquico de especies de mariposas con respecto a la tasa de ocurrencia (proporción de sitios ocupados) se reflejaba con precisión en las submuestras temporales. El submuestreo temporal no condujo a inferencias erróneas acerca de la importancia relativa de seis variables predictivas basadas en vegetación sobre la riqueza de especies de mariposas. A pesar de la escala temporal del muestreo, la composición de especies de mariposas fue más similar en sitios con composición de especies de plantas similar. El orden jerárquico de ocurrencia de especies de mariposas en las muestras subtemporales estuvo muy correlacionado con el orden jerárquico de ocurrencia de especies en todo el conjunto de datos. Por lo tanto, se pudieron obtener inferencias similares de las asociaciones entre vegetación y mariposas y de las tasas de ocurrencia relativa de especies individuales de mariposas con muestreo temporal menos intensivo o extensivo. Si se deben hacer compromisos entre la intensidad y extensión de muestreo temporal, nuestros resultados sugieren que la maximización de la extensión temporal capturará la variación en interacciones bióticas y ocurrencia de especies más adecuadamente. [source]

Grazing Intensity and the Diversity of Grasshoppers, Butterflies, and Trap-Nesting Bees and Wasps

CONSERVATION BIOLOGY, Issue 6 2002
Andreas Kruess
The reduction of management intensity can be a useful tool for the long-term conservation of the biological diversity of grasslands. We analyzed floral and faunal diversity on intensively and extensively (unintensively) grazed pastures and on 5- to 10-year-old ungrazed grasslands in northern Germany. Each of the three grassland habitats differing in grazing intensity was replicated six times. We related diverse taxa such as grasshoppers, butterfly adults and lepidopteran larvae, and trap-nesting solitary bees and wasps to vegetation structure. There was an increase of species richness and abundance from pastures to ungrazed grasslands. The percentage of parasitism of the most abundant trap-nesting species, the digger-wasp ( Trypoxylon figulus), was also higher on ungrazed grasslands. Decreased grazing on pastures enhanced species richness for adult butterflies only, whereas the abundance of adult butterflies, solitary bees and wasps, and their natural enemies increased. Although the differences in insect diversity between pastures and ungrazed grassland could be attributed to a greater vegetation height and heterogeneity ( bottom-up effects) on ungrazed areas, the differences between intensively and extensively grazed pastures could not be explained by changes in vegetation characteristics. Hence, intensive grazing appeared to affect the insect communities through the disruption of plant-insect interactions. A mosaic of extensively grazed grassland and grassland left ungrazed for a few years may be a good means by which to maintain biodiversity and the strength of trophic interactions. Resumen: El mantenimiento de pastizales como hábitats distintos depende del manejo regular, generalmente, por medio de pastoreo o segado, pero se sabe que la diversidad de especies declina con el incremento de intensidad de manejo. La reducción de la intensidad de manejo puede ser una herramienta útil para la conservación a largo plazo de la biodiversidad de pastizales. Analizamos la diversidad florística y faunística en pastizales pastoreados intensiva y extensivamente (no intensivos) y en pastizales de 5 a 10 años no pastoreados en el norte de Alemania. Cada uno de los tres hábitats de pastizal diferentes en el grado de pastoreo fue replicado seis veces. Relacionamos diversos taxones como chapulines, mariposas adultas, larvas de lepidópteros y abejas y avispas solitarias con la estructura de la vegetación. Hubo un incremento en la riqueza y abundancia de especies de pastizales pastoreados a no pastoreados. El porcentaje de parasitismo de la especie de avispa más abundante ( Trypoxylon figulus) también fue mayor en pastizales no pastoreados. La reducción del pastoreo incrementó la riqueza de especies de mariposas adultas solamente, mientras que incrementó la abundancia de mariposas adultas, abejas y avispas solitarias y sus enemigos naturales. Aunque las diferencias en la diversidad de insectos entre pastizales pastoreados y no pastoreados pudiera atribuirse a la mayor altura de la vegetación y a la heterogeneidad (efectos abajo-arriba) en áreas no pastoreadas, las diferencias entre pastizales pastoreados intensiva y extensivamente no podría explicarse por cambios en las características de la vegetación. Por consiguiente, el pastoreo intensivo aparentemente afectó a las comunidades de insectos por la disrupción de las interacciones planta-animal. Un mosaico de pastizales pastoreados extensivamente y pastizales sin pastoreo por varios años puede ser una buena estrategia para mantener la biodiversidad y la vigencia de las interacciones tróficas. [source]

Rhodolith bed diversity in the Gulf of California: the importance of rhodolith structure and consequences of disturbance

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2003
D.L. Steller
Abstract 1.Rhodolith beds, unattached coralline reefs, support a high diversity and abundance of marine species from both hard and soft benthos. We used surveys in multiple shallow (3,20 m) beds in the Gulf of California to (1) examine seasonal patterns in associated floral and faunal diversity and abundance, (2) compare differences in faunal associations between rhodolith beds and adjacent sedimentary habitats, (3) examine the importance of complexity of rhodolith structure to community structure, and (4) estimate the impact of anthropogenic disturbance on rhodoliths and associated species. 2.Macroalgal richness was seasonal, and beds supported higher richness in winter (to 36 species) than summer (6,7 species), primarily due to foliose red algae. Strong seasonal variation in the abundance of dominant cover organisms was due to a shift from macroalgae and mat-forming colonial invertebrate species to microalgae. 3.The community in a rhodolith bed of high-density thalli (El Coyote average ,11000 thalli/ m,2) had higher richness (52 versus 30 species) and abundance of epibenthic and crypto- and in-faunal species compared with an adjacent sand community. Species diversity and abundance was particularly high for unique cryptofaunal organisms associated with rhodolith interstices. Cryptofauna reached average densities of 14.4 organisms/ cm,3 rhodolith, the majority of which were crustaceans, polychaetes and cnidarians along with rhodolith-specific chitons. 4.Results from sampling across a range of rhodolith morphs in the El Requeson bed (with lower average cryptofaunal densities of 2.3 organisms/ cm,3) revealed that the total organisms supported by a rhodolith significantly increased with both complexity (branching density) and space available (thallus volume). These data suggest that reducing the population size structure, structural complexity and cover of living rhodoliths could decrease species richness and abundance. 5.While disturbance is a natural feature of these free-living beds, increased anthropogenic disturbance from trawling, anchoring and changes in water quality can directly impact the bed community through substrate alteration. Commercial fishing threatens rhodolith beds in the Gulf of California by decreasing rhodolith size and increasing sedimentation and burial rates. In addition to reducing direct destruction, conservation efforts should also focus on decreasing practices that breakdown thalli. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Relationships among non-native plants, diversity of plants and butterflies, and adequacy of spatial sampling

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2005
ERICA FLEISHMAN
Non-native invasive species are altering ecosystems in undesirable ways, often leading to biotic homogenization and rapid reduction of evolutionary potential. However, lack of money and time hampers attempts to monitor the outcome of restoration efforts. Hence, it is useful to determine whether relatively limited sampling can provide valid inferences about biological responses to pattern-based and process-based variables that are affected by restoration actions. In the Mojave Desert, invasion of salt-cedar (Tamarix ramosissima) has altered vegetational communities and some measures of faunal diversity. We tested whether six vegetation-based predictor variables affected species richness of butterflies in the Muddy River drainage (Nevada, USA). We also explored whether similar conclusions about relationships between vegetation and butterflies could have been obtained by using data from a subset of the 85 locations included in the study. We found that the effect of non-native plants on species richness of butterflies was negligible. Availability of nectar had the greatest independent explanatory power on species richness of butterflies, followed by species richness of plants. In comparison with the full data set, subsamples including 10, 25 and 50% of sites yielded similar conclusions. Our results suggest that relatively limited data sets may allow us to draw reliable inferences for adaptive management in the context of ecological restoration and rehabilitation. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 157,166. [source]