> > stonerollers are holding their own for the most part because of their
> > nest-building and guarding strategy.
>
>Interesting. Where did you get this information? Does this account for all
>stonerollers, or just, say, the central? I ask because the range and
>abundance of the largescale stoneroller is shrinking, with the central
>stoneroller supplanting it in many areas. The central stoneroller is a more
>ecologically "plastic" species that's found in a wider array of stream
>conditions; as such it may be better capable of modifying its breeding
>behavior to successfully spawn when stream conditions (e.g., temperature)
>change as a result of human modification. In contrast, the largescale
>stoneroller is less tolerant of reduced flow, turbidity, and silt. In
>agricultural areas of Iowa, Illinois and southern Wisconsin, where stream
>modifications are often the most acute, the largescale stoneroller has been
>or is likely to be extirpated from streams in which it sympatrically occurs
>with its more adaptable cousin. In the Ozarks of Missouri and Arkansas,
>where habitats are less disturbed and water quality is higher, the
>largescale stoneroller thrives and is apparently secure.
>
>
>Chris Scharpf
>Baltimore
Again, I was speaking in broad stroke. You mention the area--Iowa, Illinois,
s. Wisconsin--where largescale stonerollers (_Campostoma oligolepis_ vs. _C.
anomalum_, central) are considered to be "vulnerable" or "of special
interest" because they're more sensitive to habitat degradation from land
use changes. I saw the summary of state designations of status on
NatureServe, an online encyclopedia of natural history. It has a very
powerful species search on it which leads to reasonably well researched
species summaries. For _oligolepis_ it shows them vulnerable in those three
states; but it also seems to report that _oligolepis_ isn't found in
Tennessee, which isn't the case. And you're right, it seems that _anomalum_
(probably still an unresolved species complex with at least three
subspecies) is more of a generalist.
In the whole web of adaptations to ecological niches that defines species,
an ability to maintain a consistent level of reproductive success is very
important (and fairly easy for us to compare between species). But then,
tolerances to pulses of lowered water oxygen, temperature tolerances, pH
tolerances... are also important.
--Bruce Stallsmith
Huntsville, AL, US of A
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