One of the
researchers’ motives for conducting this research that there is a lack of
understanding of the processes (dispersal, speciation and environmental filtering)
that play a role in creating the global patterns of plant diversity. Other
motive that was mentioned in the introduction is that the studies that have
been conducted on the phylogenetic patterns have not been on a large spatial
scale, but only on terrestrial vertebrates and have been descriptive studies.
These factors lead the researchers to conduct their study because there is a
lack of research done on their topic.
main objective was to understand how dispersal and environmental filtering and
in-situ speciation influence global patterns of diversity. They planned to look
at 3 plant groups to investigate the effects of abiotic characteristics related
to the 3 processes. They created 4 hypotheses for their research. H1 tested the
claims they had regarding to group differences, H2 looked at dispersal
filtering, H3 looked at environmental filtering and H4 tested in-situ
drawn from the research is that their research showed that differences in in
the 3 plant groups shows that “drivers of phylogenetic structure have strong
group-specific components” which supported H1. For H2, the palms plant group
supported their claim by showing that there is a negative effect of island
isolation phylogenetic diversity. Which was their original claim. The research
on angiosperms rejected H2 because of the positive relation of phylogenetic
diversity to island isolation. The results of the fern plant group rejected H2
because it showed that island isolation and geologic history were unimportant.
The research supported H3 by showing the importance of environmental filtering
for the phylogenetic structure of island floras. H4 was supported for both the
angiosperms and the palm groups. There was only partial support of H4 when conducting
the research on ferns.
The support the
author used to show that H1 was supported was percentages showing the how much
environmental predictors explained variation in the phylogenetic structure.
There was a 49% for angiosperms, 42% for palms and only 18% for ferns. The
difference in percentages went to further prove that group differences affect
global patterns and phylogenetic structure. The results that showed that the absence
of palm lineages on remote islands supported the H2 claim that there is a negative
effect of island isolation on phylogenetic diversity. The results that rejected
H2 for angiosperms showed that there was an increase in phylogenetic diversity with
increasing isolation. The results showed that H2 was rejected when looking at
the ferns. The reasoning behind this, according to the researchers, was because
of the small spores and the high dispersal rate of the ferns. The results that
supported H3 showed different climatic factors and how they affected each plant
group. The angiosperms showed a negative effect of island area on angiosperm
phylogenetic diversity and this supported hypothesis H4. Same for palms, island
area has a negative effect on phylogenetic diversity, which gives support for
One of the main
conclusion drawn by the researchers are that the 3 processes (dispersal
filtering, environmental filtering and in-situ speciation) leave strong signals
in the phylogenetic structure of island groups. The other main conclusion
mentioned was that the researchers’ discoveries gave insight to how plant
diversity originated and show the importance of the 3 processes that were
researched for generating global plant diversity patterns.
The implications of
the research that the researchers mentioned were about future research. They stated
that further research should involve information on dispersal traits on the in-situ
speciation and on species distributions to look at the importance of assembly
processes. The researchers also mentioned how their approach on the study
allows predictions to be made on the topic of how “assembly processes act along
large-scale environmental gradients”.
According to the researchers,
some factors that weaken the results of the study are that the environmental
factors that were looked at by the researchers affect more than one of the
processes that were studied. Another factor is that looking at a larger species
pool is not as insightful as looking at a smaller region species pool when analyzing
the phylogenetic structure of island assemblages in certain regions.