14 research outputs found
Lake macroinvertebrates and the altitudinal environmental gradient in the Pyrenees
14 páginas, 6 tablas, 2 figuras.The distribution of different macroinvertebrate
groups inhabiting the littoral zone of 82
mountain lakes in the Pyrenees was investigated in
relation to the altitudinal environmental gradient. For
each lake, altitude, longitude and latitude, together
with 28 environmental variables, relating to chemical
and physical characteristics and to lake general
productivity, were considered. Using Principal Component
Analysis (PCA) we showed that the altitudinal
environmental gradient (i.e. altitude and altituderelated
variables) represented the largest gradient of
environmental variability. We found that incidence
was related to altitude in about 50% of macroinvertebrate
groups, most relationships being inverse, and
also that the number of macroinvertebrate groups
found per lake was better described by a second-order
polynomial function than by simple linear regression.
However, this relationship was linear for a subset of
high-altitude lakes above 2,500 m a.s.l., suggesting
an ecological threshold around this altitude. Redundancy
Analyses (RDAs) showed the importance of
environmental factors varying with altitude for the
distribution of macroinvertebrate groups. Organic
matter, salmonid presence, fine substrate dominance,
macrophyte coverage, temperature and altitude by
itself were, in this order, the most relevant factors.
Partial RDAs showed that different combinations of
these variables contributed to the explanation of the
distribution of each group. However, the variable that
uniquely explained most variability differed from
group to group. We conclude that the altitudinal
gradient is a multi-faceted ecological factor, which
impinges on each group by means of some specific
environmental variable(s) that are particularly
relevant for the life history of that group.The field work of this study was financed by grants from the Academy of Finland to
J. Heino and T. Muotka.Peer reviewe