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Poor Dispersal Abilities (poor + dispersal_ability)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Distribution of rotifer assemblages in North Island, New Zealand, lakes: relationships to environmental and historical factors

FRESHWATER BIOLOGY, Issue 2 2002
Ian C. Duggan
1.,The geographical distribution of planktonic rotifer species was investigated in 31 lakes in the North Island of New Zealand. 2.,A total of 78 species was recorded. Species richness, previously thought to be low in New Zealand, was found to be comparable with that of northern temperate lakes with an average of 21.1 species found per lake. The large, deep oligotrophic Lake Taupo had the lowest richness, and the artificial reservoirs the highest. 3.,The distribution of species, investigated using multivariate techniques [Cluster analysis, canonical correspondence analysis (CCA)], was most strongly associated with trophic state gradients. For example, Conochilus unicornis, C. dossuarius and Ascomorpha ovalis were associated with more oligotrophic conditions, and Brachionus budapestinensis, B. calyciflorus and Keratella tropica with more eutrophic conditions. Inorganic turbidity was also of importance in determining rotifer distributions in some shallower lakes. 4.,Some species, for example K. australis and C. exiguus, appear to be limited in distribution by poor dispersal abilities. [source]

Contemporary habitat loss reduces genetic diversity in an ecologically specialized butterfly

JOURNAL OF BIOGEOGRAPHY, Issue 7 2010
Neil Collier
Abstract Aim, This study investigated the influence of contemporary habitat loss on the genetic diversity and structure of animal species using a common, but ecologically specialized, butterfly, Theclinesthes albocincta (Lepidoptera: Lycaenidae), as a model. Location, South Australia. Methods, We used amplified fragment length polymorphism (AFLP) and allozyme datasets to investigate the genetic structure and genetic diversity among populations of T. albocincta in a fragmented landscape and compared this diversity and structure with that of populations in two nearby landscapes that have more continuous distributions of butterflies and their habitat. Butterflies were sampled from 15 sites and genotyped, first using 363 informative AFLP bands and then using 17 polymorphic allozyme loci (n = 248 and 254, respectively). We complemented these analyses with phylogeographic information based on mitochondrial DNA (mtDNA) haplotype information derived from a previous study in the same landscapes. Results, Both datasets indicated a relatively high level of genetic structuring across the sampling range (AFLP, FST = 0.34; allozyme, FST = 0.13): structure was greatest among populations in the fragmented landscape (AFLP, FST = 0.15; allozyme, FST = 0.13). Populations in the fragmented landscape also had significantly lower genetic diversity than populations in the other two landscapes: there were no detectable differences in genetic diversity between the two continuous landscapes. There was also evidence (r2 = 0.33) of an isolation by distance effect across the sampled range of the species. Main conclusions, The multiple lines of evidence, presented within a phylogeographic context, support the hypothesis that contemporary habitat fragmentation has been a major driver of genetic erosion and differentiation in this species. Theclinesthes albocincta populations in the fragmented landscape are thus likely to be at greater risk of extinction because of reduced genetic diversity, their isolation from conspecific subpopulations in other landscapes, and other extrinsic forces acting on their small population sizes. Our study provides compelling evidence that habitat loss and fragmentation have significant rapid impacts on the genetic diversity and structure of butterfly populations, especially specialist species with particular habitat preferences and poor dispersal abilities. [source]

Turnover in flightless invertebrate species composition over different spatial scales in Afrotemperate forest in the Drakensberg, South Africa

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2009
Charmaine Uys
Abstract An understanding of species turnover at different spatial scales and the influence of environmental variables including distance are important for conservation planning and management. Ground dwelling, flightless invertebrates have poor dispersal abilities and other taxa may not be effective as surrogates. This is an important consideration for biodiversity conservation in Afrotemperate forests of the Drakensberg Mountains, South Africa, where flightless invertebrates are geographically isolated by the naturally fragmented state of forests. Seventeen Afrotemperate forests in four reserves across the Drakensberg were sampled using soil and leaf litter sampling, pitfall traps, active search quadrats and tree beats. Seventy-two species were recorded, comprising 31 mollusc, nine earthworm, one onychophoran, six centipede, twelve millipede and thirteen ant species. Canonical correspondence analysis indicated that latitude (distance); fire history (disturbance) and mean annual precipitation were the most important factors governing invertebrate assemblage composition. ,sim measurements detected change in species at all spatial scales investigated, but no clear trends were evident. Distance or spatial scale alone does not explain species turnover and community composition. Effective selection of target areas, therefore, requires species level information to identify species of special concern. Résumé Une bonne compréhension de la rotation des espèces à différentes échelles spatiales et de l'influence des variables environnementales, y compris de la distance, est importante pour la planification et la gestion de la conservation. Les invertébrés qui vivent dans le sol, ceux qui ne volent pas, n'ont que de faibles capacités de se disperser, et d'autres taxons peuvent ne pas être des substituts efficaces. Ceci pourrait être une réflexion importante pour la conservation de la biodiversité dans les forêts afro-tempérées des monts Drakensberg, en Afrique du Sud, où des invertébrés qui ne volent pas sont isolés géographiquement par l'état naturellement fragmenté des forêts. On a prélevé des échantillons dans 17 forêts afro-tempérées, dans quatre réserves du Drakensberg, en utilisant des échantillons de sols et de litière de feuilles, des pièges, la recherche active dans des quadrats et le battage d'arbres. On a enregistré 72 espèces comprenant 31 mollusques, neuf vers de terre, un onychophore, six centipèdes, 12 mille-pattes et 13 fourmis. L'analyse canonique des correspondances a indiqué que la latitude (distance), l'historique des feux (perturbations) et les précipitations annuelles moyennes étaient les facteurs les plus importants pour la composition des assemblages d'invertébrés. Des mesures de ,sim ont détecté des changements d'espèces dans toutes les échelles spatiales étudiées, mais aucune tendance nette n'était visible. L'échelle de distance ou d'espace n'explique pas seule la rotation des espèces et la composition de la communauté. La sélection effective de zones cibles requiert donc des informations au niveau des espèces pour pouvoir identifier les espèces dont le statut est particulièrement inquiétant. [source]

Patch Occupancy and Potential Metapopulation Dynamics of Three Forest Mammals in Fragmented Afromontane Forest in South Africa

CONSERVATION BIOLOGY, Issue 4 2000
Michael J. Lawes
We recorded patch occupancy of blue duiker ( Philantomba monticola), tree hyrax ( Dendrohyrax arboreus), and samango monkey (Cercopithecus mitis labiatus) in 199 forest patches. Their rarity is ascribed to the fragmentation and destruction of their forest habitat. Incidence functions, derived from presence and absence data, were formulated as generalized linear models, and environmental effects were included in the fitted logistic models. The small and mostly solitary hyrax and duiker persisted in smaller patches than the large and social monkey. Although this result follows expectations based on relative home-range sizes of each species, the incidence probability of the samango monkey was invariant with increasing isolation, whereas a gradual decrease with increasing isolation was observed for the hyrax and duiker. Group dynamics may inhibit dispersal and increase the isolation effect in social species such as samango monkeys. A mainland-island metapopulation model adequately describes patterns of patch occupancy by the hyrax and duiker, but the monkeys' poor dispersal ability and obvious area-dependent extirpation suggest that they exist in transient, nonequilibrium (declining) metapopulations. Through identification of large forest patches for careful protection and management, the survival of all three species,especially the monkey,could be prolonged. Because no functional metapopulation may exist for the monkey, however, this is an emergency measure. For the duiker and hyrax, larger patches should form part of a network of smaller and closer patches in a natural matrix. Resumen: Investigamos la persistencia de tres mamíferos forestales raros de tamaño mediano (2,9 kg) en los bosques fragmentados de cinturón de niebla Podocarpus en la región central de la provincia KwaZulu-Natal, Sudáfrica. Registramos la ocupación del duiker azul ( Philantomba monticola), el hyrax arborícola ( Dendrohyrax arboreus) y el mono samango (Cercopithecus mitis labiatus) en 199 parches forestales. Su rareza se atribuye a la fragmentación y destrucción de su hábitat forestal. Las funciones de incidencia, derivadas de datos de presencia y ausencia, fueron formuladas como modelos lineales generalizados, y los efectos ambientales fueron incluidos en los modelos logísticos ajustados. Los pequeños y mayormente solitarios hyrax y duiker persistieron en parches más pequeños que los monos, que son más grandes y más sociables. A pesar de que este resultado obedece a expectativas basadas en tamaños de rango de hogar relativos de cada especie, la probabilidad de incidencia del mono samango no cambió con un incremento en el aislamiento, mientras que una disminución gradual al crecer el aislamiento se observó en hyrax y duiker. Las dinámicas de grupos podrían inhibir la dispersión e incrementar el efecto de aislamiento en especies sociables como lo es el mono samango. Un modelo de metapoblación continente-isla describe adecuadamente los patrones de la ocupación de parches por hyrax y duiker; sin embargo, la pobre capacidad de dispersión de los monos y la obvia extirpación área-dependente sugiere que estos existen en metapoblaciones transitorias, desequilibradas (en disminución). Mediante la identificación de parches forestales grandes para la protección y manejo cuidadosos, la supervivencia de las tres especies ( pero especialmente la de los monos) podría ser prolongada. Sin embargo, debido a que no existen metapoblaciones funcionales de monos, esta es una medida de emergencia. Para el duiker y el hyrax, los parches grandes deberán formar parte de una red de parches más pequeños y más cercanos en una matriz natural. [source]