Competition for food, literature question

John Shuey jshuey at
Thu May 11 14:22:19 EDT 2000

Way back when, when I was a graduate student, I became intrigued by the issue of
competition, ghosts of competition past, and experimentally testing the idea. I
never liked Clench's paper much, and was simply appalled at how often it got
cited as a "proof of competition" and its role in niche partitioning. Clench
simply noticed that hesperiinae flight periods were staggered through the
season, and inferred that this staggered emergence was the result of competition
for nectar resources, without even mentioning host phenology, nutritional
ecology or the weedy nature of the skipper species themselves.  Hence, when
Ehrlich (Biology of Butterflies 1984 pg 39) used the paper favorably to support
the concept, I couldn't take it any longer.

Nineteen years is a long time to wait to refute a paper, but I was only nine
year old when Clench published his.  I got to it as fast as I could.

As an epilogue, I designed a pretty bad study myself to look at the issue.  I
used a "guild" of sedge feeding butterflies (Euphyes dion, Euphyes conspicua,
Poanes viator and Poanes massasoit) that all fly at the same time in the same
habitat.  Although I still don't know what it means, here is what I found out.

1: Flower visitation is not random.  Certain rare flowers were preferentially
visited relative to more common flowers

2: Although there was considerable overlap in the flowers used, each skipper
species differed significantly from the other species in the proportions (or
ratios) of flower species they preferred.

3: During the two years (at a single site) that I conducted the study, the
differences between species were consistent, but within species, the pattern was
the same in both years.

I'm still pondering all this (16 years after the data were collected), but it
seems to me that this could be evidence that adult resource use (flower
visitation preferences), has an underlying genetic basis that could indeed be
shaped by interspecific competition (among other things).

Needs more data / needs more thought.


ewilliam at wrote:

> Clench's interpretation has been challenged because the skipper community
> he described did not exist as a long-time interactive community.  See Shuey
> 1986(87), J. Res. Lepid. 25(3):202-206.  Since John is active on this list,
> perhaps he might like to comment further.
> Ernest Williams
> >       Norbert Kondla asked:
> >
> >
> >> Anyone out there that can share some references with data to show
> >> population limitation due to food supply (amount).
> >
> >       This is not exactly _data_, but it might be worth checking the paper
> >'Temporal dissociation and population regulation in certain Hesperiine
> >butterflies' by Harry Clench (Ecology 48:1000-1006, 1967). Clench posits
> >temporal dissociation as a mechanism for distributing the demand on a
> >limited supply of nectar.
> >
> >       It should be noted, however, that temporal dissociation also exists
> >in _Clossiana_ in the high arctic, where plants are competing for pollin-
> >ators, rather than insects competing for nectar.
> >
> >                                               Ken Philip
> >fnkwp at

John Shuey
Director of Conservation Science
Indiana Office of The Nature Conservancy

phone:  317-923-7547
fax:  317-923-7582
email:  Jshuey at

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