100 Influential Papers - page 28

Southwood, T.R.E. (1961)
The number of insect species associated with
various trees.
Journal of Animal Ecology, 30, 1-8.
Macroecology
‘ is a non-experimental, statistical investigation
of species’ ecology and evolution, or in simple terms a search for
patterns in nature, primarily achieved by mining existing large-scale
data sets [Brown,J.H.
Macroecology
. University of Chicago Press (1995)]. Bafflingly,
this study by Southwood, the first widely available paper to use what was undoubtedly
a macroecological approach is not even cited by Brown. Southwood’s question was:
’Why do some species of plants host more species of insects than others?’ In 1960 he
had attempted to answer the question for Hawaiian trees, and then applied the same
ideas to UK trees and their associated insects in 1961. Using existing species-lists he
argued that the number of insects associated with a tree is proportional to the tree’s
recent abundance, and offered a theoretical explanation based on ‘encounter rates’
over evolutionary time [for a succinct summary of his ideas see Southwood (1973)
Symposium of the Royal Entomological Society of London
,
6
, 3-30]. By modern standards
of statistical rigour these early, pioneering forays into macroecology can easily be
criticised. What cannot be criticised is Southwood’s vision for an approach to ecology
that did not become fashionable for another 30 years.
John Lawton
Frankie, G.W., Baker, H.G. & Opler, P.A. (1974)
Comparative phenological studies of trees in tropical wet and dry
forests in the lowlands of Costa Rica.
Journal of Ecology, 62, 881-919.
A major growth area in community ecology during the latter part of the 20th century
involved investigation of the phenology and reproductive biology of tropical ecosystems,
particularly in the Neotropics. Gordon Frankie, Herbert Baker and Paul Opler were
among the early pioneers in this field, initiating detailed comparative studies of the
phenology of tropical forests in Costa Rica. In this classic paper, which has been cited
>600 times, they report on an exhaustive analysis of leafing, flowering and fruiting
periodicities of 298 tree species at wet and dry forest sites. Significantly, and in contrast
to most earlier work, the authors interpret the phenological patterns that they observed
not only in terms of climatic factors, particularly the timing and duration of the wet
and dry seasons, but also in the context of plant-animal interactions, especially pollen
and seed dispersal agents. They make the important point that climatic triggers are
most often best viewed as proximate factors eliciting phenological responses, but
that the ultimate (adaptive) explanations for the timing of these events probably
reside in beneficial plant-animal interactions associated with flowering and fruiting.
Distinguishing between proximate and ultimate factors governing adaptive trait
variation is today commonplace and lies at the heart of modern evolutionary ecology.
Spencer C.H. Barrett
S ECT I ON S I X
S P EC I E S I NT E RACT I ONS
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56
Mack, R. & Harper, J.L. (1977)
Interference in dune annuals:
spatial pattern and neighbourhood
effects.
Journal of Ecology, 65, 345-
363.
Back in 1977, plant population biology was
a nascent subject, built from the borrowed
parts of other disciplines. Harper published
his foundational
Population Biology of Plants
that year and it is notable how much of
the book came from agriculture, forestry
and horticulture. The paper is a reminder
that Harper was struggling to establish an
independent discipline, shorn of zoocentric
concepts like ‘competition’ (Harper
preferring the term ‘interference’). Mack &
Harper is an experimental demonstration
that ‘density,’ a central concept in population
biology, is not well-suited to plants. As
Mack and Harper put it, “ ‘density’ is a very
crude measure of the state of a population
or the conditions met by the individuals.
The individual plant does not react to the
density of its population but to the activity
of some of its neighbours.” They describe
experiments demonstrating that up to 69%
of the variance in target plant weight is
accounted for by the size, angular dispersion
and distance of neighbours. Directly or
indirectly, this result inspired many others
to fit individual-based models to the growth
and dynamics of plant populations - a
technique that has become standard in plant
population biology today.
Jonathan Silvertown
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TRE Southwood
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