Search results for "species diversity."
showing 10 items of 160 documents
Temporal and spatial fluctuations in moisture affect humus microfungal community structure in microcosms
2000
The effects of temporal and spatial fluctuations in moisture on the microfungal community were studied in birch litter plus pine humus microcosms over 6 months. Two treatments were used: a uniform treatment in which moisture was maintained at the original moisture content throughout the profile over the course of the experiment; and a fluctuating moisture treatment in which the moisture content of the whole microcosm fluctuated weekly around the original moisture content. At 6 months, fungal species richness was higher and diversity was lower under moisture fluctuations than under uniform moisture. The number of fungal isolates and proportional diversity was significantly higher in the bott…
Inferring the Relative Resilience of Alternative States
2013
Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear. We analyzed time series of phytoplankton communities at three sites in a floodplain in central Spain to assess the dominant frequencies or "temporal scales" in community dynamics and compared the patterns between a wet and a dry alternative state. The identified frequencies and cross-scale structures are expected to arise from positive feedbacks that…
First Record of the Nematode Physaloptera squamatae in the Helminth Community of the Introduced Anole Anolis grahami (Polychrotidae) on Bermuda
2021
The gastrointestinal helminth communities of five populations of Anolis grahami, an introduced anole on Bermuda, were surveyed to determine the prevalence, abundance, and species diversity of parasites in these reptiles. Only three nematode species were found, Atractis scelopori, Parapharyngodon cubensis, and Physaloptera squamatae. This species, P. squamatae, is recorded for the first time in Anolis grahami on Bermuda, probably introduced through its arthropod intermediate host. The role of the host A. grahami as a “spillover” agent for these parasites is discussed.
The role of landscape, topography, and geodiversity in explaining vascular plant species richness in a fragmented landscape
2016
We explained vascular plant species richness patterns in a 286 km(2) fragmented landscape with a notable human influence. The objective of this study was two-fold: to test the relative importance of landscape, topography and geodiversity measures, and to compare three different landscape-type variables in species richness modeling. Moreover, we tested if results differ when only native species are considered. We used generalized linear modeling based variation partitioning and generalized additive models with different explanatory variable sets. Landscape and topography explained the majority of the variation but the relative importance of topography and geodiversity was higher in explainin…
Helminth infracommunities of a population of the Gran Canaria giant lizard Gallotia stehlini
2004
AbstractA survey of gastro-intestinal helminth communities of Gallotia stehlini (Sauria: Lacertidae) from Gran Canaria island (Canary Archipelago, Spain), was conducted to determine the prevalence, abundance and species diversity of intestinal parasites in these lizards. Pharyngodonid nematodes were the most common intestinal helminths, three species being Gallotia specialists. Helminth infracommunities of G. stehlini were rich and appear to be closer to the interactive end of the continuum isolationist–interactive helminth communities, according to the high values of helminth diversity. It is the first case of a saurian reptile showing this kind of diverse helminth infracommunity, produced…
Spatial patterns of disparity and diversity of the Recent cuttlefishes (Cephalopoda) across the Old World
2003
Aim Diversity and disparity metrics of all Recent cuttlefishes are studied at the macroevolutionary scale (1) to establish the geographical biodiversity patterns of these cephalopods at the species level and (2) to explore the relationships between these two metrics. Location Sampling uses what is known about these tropical, subtropical and warm temperate cephalopods of the Old World based on a literature review and on measurements of museum specimens. Some 111 species spread across seventeen biogeographical areas serve as basic units for exploring diversity and disparity metrics in space. Methods Landmarks describe the shape of the cuttlebone (the inner shell of the sepiids) and difference…
Phylogeny and Biogeography of <I>Epimedium</I>/<I>Vancouveria</I> (Berberidaceae): Western North American - East Asian Disjun…
2007
Using ITS and atpB-rbcL spacer sequences of 38 (of 55) species of the highly disjunct Eurasian/North African Epimedium and all three species of its western North American sister genus Vancouveria, we reconstructed the phylogeny of these two genera and dated major splits with a molecular clock approach. Epimedium was found to be monophyletic with a stem age dated to between 9.7 and 7.4 million years ago (My). Within Epimedium, almost all sections as recognized in the most recent classification of the genus were found to be monophyletic but subg. Epimedium was found to be paraphyletic in relation to subg. Rhizophyllum. Range formation in Eurasia proceeded as follows: in a first step, the west…
Parasite communities as indicators of recovery from pollution: parasites of roach (Rutilus rutilus) and perch (Perca fuviatilis) in central Finland.
2003
We compared parasite communities in fish taken from a polluted lake (L. Vatia) and two control lakes before (1986) and after (1995) nine years of markedly reduced chemical and nutrient loading from a pulpmill in central Finland. Discriminant analyses of the 1995 data, using a function based on the 1986 data, showed that the parasite communities in the fish from the two control lakes had changed relatively little, whereas those from L. Vatia had converged on those from the mesotrophic control lake, indicating substantial recovery from the effects of pollution. Only a few species of parasites provided evidence for recovery. These were anodontid glochidia, which had increased markedly in perch…
Perch (Perca fluviatilis L.) parasites reflect ecosystem conditions: a comparison of a natural lake and two acidic reservoirs in Finland.
2000
Parasite communities of perch were studied in a natural lake (Vetamajarvi) and two reservoirs (the Kyrkosjarvi and Liikapuro reservoirs) located in Western Finland. All water bodies studied are small, shallow and humic. However, the reservoirs are more acidic than the lake (pH 5.9 and 5.3 vs. 6.4). Altogether, 18 parasite species were found, but the component communities were reduced in the harsh conditions of the reservoirs (12 and six species) as compared with the lake (17 species). In addition, the mean number of metazoan parasite specimens per fish was markedly lower in the reservoirs (64.3 and 14.3 specimens) than in the lake (116.1 specimens). Our prediction on the depauperation of pa…
Helminth parasitizing <em>Iberolacerta cyreni</em> (Müller et Hellmich, 1937) from Gredos Mountains, Iberian Peninsula
2017
A survey of the helminth communities of a population of Iberolacerta cyreni (Müller et Hellmich, 1937), a small lizard endemic to Sistema Central (Iberian Peninsula), was conducted to determine the prevalence, abundance and species diversity of parasites of these reptiles. Four species of helminths were found, one trematode, Plagiorchis molini Lent et Freitas, 1940, one cestode, Nematotaenia tarentolae López-Neyra, 1944, and two nematodes, Skrjabinelazia sp. and Spauligodon carbonelli Roca & García-Adell, 1988. Helminth infracommunities of I. cireny showed very low values of abundance and species richness and diversity, being similar to other European lizards. The parasites found seem t…