E. Marsh-matthews et Wj. Matthews, Geographic, terrestrial and aquatic factors: which most influence the structure of stream fish assemblages in the midwestern United States?, ECOL FRESHW, 9(1-2), 2000, pp. 9-21
Effects of environmental or landscape factors on species composition, speci
es richness and complexity of fish assemblages were examined using our coll
ections of fish from 65 sites on streams in 13 drainages across the midwest
ern United States. Effects of environmental factors were examined at three
scales: broad geographic factors included drainage, latitude, and longitude
; local terrestrial factors included features of the riparian zone adjacent
to the collecting site as well as local climate and land use; within-strea
m aquatic factors related to structure and hydrology of the stream reach sa
mpled. Each assemblage property was examined for its relationship to factor
s at each scale separately, and then for relative importance of all factors
found to be significant in the separate analyses. Assemblage composition (
summarized as sample scores on two axes of a detrended correspondence analy
sis) varied significantly as a function of factors at all three scales when
each scale was considered separately. With simultaneous consideration of a
ll scales, however, only broad geographic factors (particularly latitude) a
nd local terrestrial factors explained significant variation in assemblage
composition. Species richness (the number of species we captured) was expla
ined by longitude and within-stream aquatic factors both when considered se
parately and together. Assemblage complexity (quantified as slope of relati
ve abundance versus rank abundance) was only related to within-stream aquat
ic factors. Assemblage composition and emergent assemblage properties (rich
ness and complexity), therefore, were explained by factors acting at differ
ent scales. The total variation explained for assemblage composition was mu
ch greater than that explained for emergent assemblage properties, suggesti
ng that assemblage composition may vary more as a function of environmental
and landscape factors than do species richness and complexity.