|
Showing 1 - 3 of
3 matches in All Departments
A wide variety of plants, ranging in size from forest floor herbs
to giant canopy trees, rely on animals to disperse their seeds.
Typical values of the proportion of tropical vascular plants that
produce fleshy fruits and have animal-dispersed seeds range from
50-90%, depending on habitat. In this section, the authors discuss
this mutualism from the plant's perspective. Herrera begins by
challenging the notion that plant traits traditionally interpreted
as being the product of fruit-frugivore coevolution really are the
outcome of a response-counter-response kind of evolutionary
process. He uses examples of congeneric plants living in very
different biotic and abiotic environments and whose fossilizable
characteristics have not changed over long periods of time to argue
that there exists little or no basis for assuming that gradualistic
change and environmental tracking characterizes the interactions
between plants and their vertebrate seed dispersers. A common theme
that runs through the papers by Herrera, Denslow et at. , and
Stiles and White is the importance of the 'fruiting environment'
(i. e. the spatial relationships of conspecific and non-conspecific
fruiting plants) on rates of fruit removal and patterns of seed
rain. Herrera and Denslow et at. point out that this environment is
largely outside the control of individual plant species and, as a
result, closely coevolved interactions between vertebrates and
plants are unlikely to evolve.
Any scientific discipline needs a theoretical framework to guide
its development and to sharpen the questions its researchers
pursue. In biology, evolution is the grand theoretical framework,
and an his torical perspective is necessary to understand
present-day biological conditions. In its formative years, the
modern study of the fruit-frugivore mutualism was guided by the
'specialist-generalist' paradigm developed by D. Snow, D. McKey,
and H. Howe. Howe reviews the current status of this evolution ary
paradigm and points out that it has been dismissed by many workers
before being adequately tested. This is because ecologists working
with the tropical plants and frugivorous birds for which the
paradigm was originally developed rarely measure the seed dispersal
effectiveness of different disperser species. He indicates that
this paradigm still has heuristic value and suggests that several
additional ecological paradigms, including the concept ofkeystone
species ofplants and frugivores and the role that frugivores play
in density-dependent mortality in tropical trees, are worth
studying. The concept of seed dispersal quality has been central to
discussions of fruit-frugivore coevolution. Schupp thoroughly
reviews data bearing on this concept, constructs a hierarchical
framework for viewing disperser effectiveness, and points out that
disperser effectiveness depends on both the quantity and quality of
seed dispersal. Effectiveness, in turn, affects both evolutionary
and ecological relationships between dispersers and their food
plants."
A wide variety of plants, ranging in size from forest floor herbs
to giant canopy trees, rely on animals to disperse their seeds.
Typical values of the proportion of tropical vascular plants that
produce fleshy fruits and have animal-dispersed seeds range from
50-90%, depending on habitat. In this section, the authors discuss
this mutualism from the plant's perspective. Herrera begins by
challenging the notion that plant traits traditionally interpreted
as being the product of fruit-frugivore coevolution really are the
outcome of a response-counter-response kind of evolutionary
process. He uses examples of congeneric plants living in very
different biotic and abiotic environments and whose fossilizable
characteristics have not changed over long periods of time to argue
that there exists little or no basis for assuming that gradualistic
change and environmental tracking characterizes the interactions
between plants and their vertebrate seed dispersers. A common theme
that runs through the papers by Herrera, Denslow et at. , and
Stiles and White is the importance of the 'fruiting environment'
(i. e. the spatial relationships of conspecific and non-conspecific
fruiting plants) on rates of fruit removal and patterns of seed
rain. Herrera and Denslow et at. point out that this environment is
largely outside the control of individual plant species and, as a
result, closely coevolved interactions between vertebrates and
plants are unlikely to evolve.
|
You may like...
Tenet
John David Washington, Robert Pattinson
Blu-ray disc
(1)
R54
Discovery Miles 540
Queen Of Me
Shania Twain
CD
R195
R175
Discovery Miles 1 750
|