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6 results for “Similarity Distance Decay”
Data from: Similarity in mycorrhizal communities associating with two widespread terrestrial orchids decays with distance
Aim: Interactions with mycorrhizal fungi are increasingly recognized as an important factor underlying the distribution and abundance of orchid species. However, the geographic distribution of orchid mycorrhizal fungi (OMF) and how their communities vary over large geographical areas are less well understood. Because climatic and environmental similarity may decrease with geographical distance or because some OMF have limited dispersal capabilities, similarities in orchid mycorrhizal communities can be expected to decrease with increasing distances separating orchid populations. However, up till now empirical evidence is largely lacking. Location: Eurasia Taxa: Gymnadenia conopsea (L.) R. Brown and Epipactis helleborine (L.) Crantz Methods: High-throughput sequencing was used to perform a cross-continental comparison of OMF that associate with two widespread Eurasian terrestrial orchids, Epipactis helleborine and Gymnadenia conopsea. Both phylogenetic and non-phylogenetic measures of community dissimilarity and their components were calculated and related to geographic distances using Mantel tests. Results: Our results showed that in both orchid species similarity in mycorrhizal communities decreased significantly with geographical distance. Decomposing the contribution of spatial turnover and nestedness to overall dissimilarity showed that the observed dissimilarity was mainly the result of species replacement between regions, and not of species loss. Similarly, a strong relationship was observed between phylogenetic community dissimilarity and geographic distance. Decomposing PCD values into a nonphylogenetic and phylogenetic component showed that orchid populations located closely next to each other were likely to contain the same OTUs, but that the non-shared taxa came from different phylogenetic clades. Species indicator analyses showed that the majority of OMF OTUs were restricted to particular geographic areas. However, some OTUs occurred in both continents, indicating that some fungi have very wide distributions. Main conclusions: Overall, these results demonstrate that orchid mycorrhizal communities differ substantially across large geographic areas, but that the distribution of orchids is not necessarily restricted by the distribution of particular OMF. Hence, widespread orchid species can be considered mycorrhizal generalists that are flexible in the OMF with which they associate across large geographic areas.
Data from: Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study
In biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1) SDD is influenced by both spatial extent and sample size; (2) the potential effect of the phylogenetic level has yet to be tested; (3) the effect of a marked biogeographical structuring upon SDD patterns is largely unknown; and (4) the SDD relationship is usually explored with modern, mainly terrestrial organisms, whereas fossil taxa are seldom used in that perspective. Using this relationship, we explore the long-distance dispersal of the Early Jurassic (early Pliensbachian, c. 190.8 Ma to 187.6 Ma) ammonites of the western Tethys and adjacent areas, in a context of marked provincialism. We show that the long-distance dispersal of these ammonites is not related to shell size and shape, but rather to the environmental characteristics of the province to which they belong. This suggests that their long-distance dispersal may have been essentially driven by passive planktonic drift during early juvenile, post-hatching stages. Furthermore, it seems that the SDD relationship is not always an appropriate method to characterize the existence of a biogeographical structuring. We conducted SDD analyses at various spatial, sampling and phylogenetic scales in order to evaluate their sensitivity to scale effects. This multi-scale approach indicates that the sampling scale may influence SDD rates in an unpredictable way and that the phylogenetic level has a major impact on SDD patterns.
Data from: Untangling phylogenetical, geometrical and ornamental imprints on Early Triassic ammonoid biogeography: a similarity-distance decay study.
Ammonoids are diverse and widespread fossil shelly cephalopods that flourished in the world ocean during more than 300 million years before their total extinction, 65 million years ago. In spite of two centuries of intensive scientific studies, their mode(s) of life, and most particularly long-distance dispersal abilities remain poorly known. Here we address this question by looking at the latitudinal distribution of Early Triassic (~250 Myr) ammonoids through similarity-distance decay analyses. We examine and compare how rates of similarity-distance decay differ between various systematic, shell geometry and ornamentation groups, during the same ~3.5 myr Early Triassic time interval, in order to untangle phylogenetical, geometrical and ornamental imprints on the observed biogeographical pattern. Our data do not support any phylogenetical and shell ornamentation control on the similarity-distance decay, but rather evidence a significant effect of (sub-)adult shell geometry: most evolute morphs tend to have been more endemic than most involute ones. This result contrasts with the classical hypothesis that long-distance ammonoid dispersal mainly occurred during the earliest planktonic young stages, and thus that (sub-)adult morphological characteristics should not constrain large-scale biogeographical patterns of ammonoids. While a direct control by Sea Surface Temperature can be discarded, this result may indicate that at least some adult Triassic ammonoid morphs were good active swimmers able to achieve long-distance migrations, as observed for some present-day coleoid cephalopods.
Data from: Untangling phylogenetical, geometrical and ornamental imprints on Early Triassic ammonoid biogeography: a similarity-distance decay study.
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Data from: Similarity in mycorrhizal communities associating with two widespread terrestrial orchids decays with distance
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Data from: Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study
Open the record for dataset details and reuse information.
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