Download Nirav Patel 2/8/2011 Biogeography 1. Bartish, I.V., Hennekens, S

Nirav Patel
2/8/2011
Biogeography
1. Bartish, I.V., Hennekens, S., Aidoud, A., Hennion, F., Prinzing, A. 2010. Species pools along
contemporary environmental gradients represent different levels of diversification. Journal of
Biogeography (J.Biogeogr.) (2010) 37, 2317-2331.
Igor V. Bartish is with the University of Rennes with Unit ‘Ecobio’ in Campus Beaulieu in
Rennes, France in Baˆtiment 14A.
Stephan Hennekens is with Alterra at the Centre for Ecosystem Studies, WUR, PO Box 47,
6700AA
Wageningen, The Netherlands.
2). Looking specifically at angiosperms, to what extent can different habitat types can be
characterized as more conductive to support higher species diversities in comparison to others?
Are some habitat types characterized by taxa of higher taxonomic ranks that diversity into
subsidiary taxa? Are some habitat types distinguished by phylogenetically highy derived species,
for example species with many close relatives, while other habitats contain species that have
many relatives (characterizing high and low levels of cladogenic diversification)? Given these
differences, do current environmental gradient, reflect the position of these habitat types? Or is
the habitat totally unrelated to the levels of diversification of a particular species?, as different
positions on a habitat gradient might show the same levels of taxonomic or cladogenic
diversification.
Hypotheses tested: Habitat types differ in the levels of diversification represented in the species
pools, the differences in levels of diversification are associated with specific environmental
factors. These hypotheses were tested across the full range of angiosperm habitat types (light,
temperature, soil moisture, soil nitrogen, soil pH and biotic (grazing) conditions.
3.It is known that different habitat types within a region are characterized by different species
compositions, and species diversities vary depending on the habitat type. The presence of certain
clades within a particular environment is an example of this, and is known as niche
conservatism. Within a region it is unknown whether phylogenetic clades with high rates of
diversification, distribute non-randomly within particular habitat types, and how these nonrandom distributions associate themselves with environmental factors. The article seeks to
clarify the uncertainty surrounding the link between the present-day habitat gradients with the
levels of diversification because for conservation purposes, habitat type that have diverse taxa
can be considered to be more valuable for conservation. Second, clades that contain different
species, may interact or behave differently. These behavioral differences can account for the
alteration of the normal functioning of a given community. Lastly, if given within one particular
region, high rates of diversification within clades in a given region can be associated with
positions within environmental gradients, and if this link is consistent through time and space,
then it can be correlated that high diversification rates are tied to the environmental
characteristics associated with these habitats.
Angiosperms within the Netherlands became the focal point to test this idea, as it is
difficult to study habitat types within every single region in the world. The flora within the
Netherlands is good for the study given, the detailed records of the plant species composition
across the wide range of environmental conditions, and the availability of estimates within
Nirav Patel
2/8/2011
Biogeography
ecological parameters for abiotic environmental factors, and the availability and presence of a
highly resolved, species level, phylogenetic topology. Variation in levels of diversification
within the Netherlands became ideal as the levels of diversification within particular habitat
types is unlikely to be due to any particular in situ evolutionary processes within the region.
4) Utilizing the spatially explicit vegetation database within the Netherlands, they studied
angiosperm populations in the following lenses of considering environmental variables,
taxonomic diversification, cladogenic diversification, and statistical analyses (specifically
cladogenic diversification estimates using multiple regression analyses).
5) They found considerable taxonomic and cladogenic diversification among habitat types, and
taxonomic diversification strongly correlated with cladogenic diversification. Low soil moisture
and high luminosity were identified as strongly correlating with high taxonomic diversification.
Low soil moisture and high soil pH were associated with high cladogenic diversification.
Temperature, soil nitrogen, grazing pressure were not related to either category. Pressures like
high grazing associated with the species richness of a given community.
Nirav Patel
2/8/2011
Biogeography
6) Although they obtained this data from the historical records within reputable sources in the
Netherlands, the regional classification of habitats might exclude several important outliers and
also given the fact that the Netherlands is below sea level, could it be possible that this could
impact the diversity of habitats, this was not mentioned at all in the study.
7) Resulting from high levels of taxonomic and cladogenic variation and diversification, certain
species can accumulate in particular contemporary habitats, and these habitats are not
characterized by increased species richness. The non-random representation of high levels of
Nirav Patel
2/8/2011
Biogeography
diversification has major impacts for conservation efforts in the sense that there are constraints in
the assembly of the “tree of life” within a given habitat and gives us a better insight as to how
biodiversity works within particular environments.