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Contrarian clade confirms the ubiquity of spatial origination patterns in the production of latitudinal diversity gradients.

ABSTRACT: The latitudinal diversity gradient (LDG), wherein the number of species and higher taxa peaks in the tropics and decreases toward the poles, is the best-documented large-scale diversity pattern on Earth, but hypotheses explaining the standard LDG must also account for rare "contrarian" taxa that show diversity maxima outside of the tropics. For marine bivalves, one of the few groups that provide spatially explicit temporal data on a global scale, we show that a major contrarian group, the Anomalodesmata, unexpectedly exhibits the same large-scale dynamics as related clades having normal LDGs in two key respects. First, maxima in standing genus diversity and genus origination rates coincide spatially. Second, the strength of a clade's present-day LDG is significantly related to the proportion of its living genera that originated in the tropics during the late Cenozoic, with the contrarian gradient strength at both species and genus level predicted quantitatively by the values for the other clades. Geologic age distributions indicate that the anomalous LDG results from origination that is damped in the tropics rather than heightened in the temperate zones. The pervasive role of spatial origination patterns in shaping LDGs, regardless of the position of their diversity maxima, corroborates hypotheses based on clades showing standard gradients and underscores the insights that contrarian groups can provide into general principles of diversity dynamics.

SUBMITTER: Krug AZ

PROVIDER: S-EPMC2084308 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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Contrarian clade confirms the ubiquity of spatial origination patterns in the production of latitudinal diversity gradients.

Krug Andrew Z AZ Jablonski David D Valentine James W JW

Proceedings of the National Academy of Sciences of the United States of America 20071107 46

The latitudinal diversity gradient (LDG), wherein the number of species and higher taxa peaks in the tropics and decreases toward the poles, is the best-documented large-scale diversity pattern on Earth, but hypotheses explaining the standard LDG must also account for rare "contrarian" taxa that show diversity maxima outside of the tropics. For marine bivalves, one of the few groups that provide spatially explicit temporal data on a global scale, we show that a major contrarian group, the Anomal ...[more]

PMID: 17989214

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Project description:AimThe latitudinal diversity gradient (LDG) - in which species richness decreases from the equator toward the poles - is among the most fundamental distributional patterns in ecology. Despite the expectation that the diversity of parasites tracks that of their hosts, available evidence suggests that many parasites exhibit reverse latitudinal gradients or no pattern, yet the rarity of large-scale datasets on host-parasite interactions calls into question the robustness of such trends. Here, we collected parasitological data from a host group of conservation importance - lentic-breeding amphibians - to characterize the form and direction of relationships among latitude, parasite richness, and parasite load.LocationThe contiguous USA.Time period2000 to 2014.Major taxa studiedLentic-breeding frogs and toads and their helminth parasites.MethodsWe collected information on parasite richness and infection load for 846 amphibian populations representing 31 species. We combined these data with environmental and biological data to test for LDGs and potential mechanisms.ResultsBoth parasite richness and abundance increased across 20 degrees of latitude - a reverse LDG. For parasite richness, this pattern was partially explained by latitudinal increases in wetland area, landcover diversity, and the richness of waterbirds - which function as definitive hosts for many amphibian parasites. Host body size also correlated positively with latitude and helminth richness, potentially reflecting increased habitat availability, greater host longevity, or a persistent phylogenetic signal. Parasite abundance associated positively with wetland area and landcover diversity, but negatively with amphibian taxonomic richness. Longitude exhibited non-linear relationships with parasite abundance and richness, which we suggest stem from large-scale variation in host availability (e.g., migratory bird flyways).Main conclusionsWith growing interest in the distribution of parasites and pathogens, these results highlight the importance of inverse latitudinal gradients while emphasizing the explanatory influence of host body size, habitat availability, and host diversity.

Project description:Researchers frequently discuss spatial distribution patterns of species diversity and biomass together with their correlations along geographical gradients. Typical subalpine meadows occur widely on the east of the Loess Plateau, China; here, we selected nine mountains belonging to four mountain systems from north to south on the east of the plateau. We analyzed five latitudinal and longitudinal gradients together with six elevational gradients to study the spatial distribution patterns of species diversity (including ?, ?, and ? diversity) and biomass plus with their relationships at various scales. Results showed that (1) for diversity, ?-Diversity manifested unimodal variation patterns in horizontal spaces, peaking at high latitude and low longitude. However, ?-diversity was not sensitive to elevation in vertical spaces and tended to decrease with increasing elevation. With increased latitude, longitude, and elevation, ?-Diversity diminished; meanwhile, the rate of species turnover decreased and the similarity of community composition enlarged. ?-Diversity demonstrated quadratic function changes that were initially incremental and then decreased with increasing longitude, elevation, and latitude from 37.5° to 40°. In general, ?-diversity had positive correlation with ?-diversity and negative correlation with ?-diversity, which conformed to the function of ? = ?/?. (2) For biomass, changes of aboveground biomass (AB) were more obvious along latitudinal gradients, whereas variations of belowground biomass (BB) had smaller differences along longitudinal and latitudinal gradients. More biomass was allocated to BB toward the north and east, whereas root-to-shoot ratio (R/S) was more evident at greater latitude than greater longitude. With increased elevation, more biomass was also allocated to BB, and the relationship of biomass to elevation was closer in AB. In short, the relation of biomass allocation tended to belowground plant parts with different geographical scales. (3) Species diversity had the strongest positive influence on AB. The Patrick and Shannon indices had correlations of power functions with AB and R/S, respectively, indicating that an allometric model could be used to model relationships between species diversity and biomass. In conclusion, the unique geomorphological structures with a series of basins between mountain systems on the east of the Loess Plateau, meant that subalpine meadows were mostly distributed along latitudinal directions, so the spatial distribution of species diversity and biomass was more evident along latitudinal gradients, and thus the response of aboveground biomass was more sensitive to variations of spatial gradients and species diversity.

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Contrarian clade confirms the ubiquity of spatial origination patterns in the production of latitudinal diversity gradients.

Publications

Contrarian clade confirms the ubiquity of spatial origination patterns in the production of latitudinal diversity gradients.

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