Differences In Evolutionary Biology

Introduction
A key concept in evolutionary biology is that divergent selective regime will often generate and maintain some type of phenotypic diversity (Langerhans et al. 2003). This divergent selection can lead to differences in phenotypic expression either by a genetic differentiation or phenotypic plasticity (Levins, 1968; West-Eberhard, 1989: Robinson and Wilson, 1994; Orr and Smith, 1998; Schluter, 2000; cited in Langerhans, 2003). Such divergence is significant as it can influence microevolutionary changes and result in speciation (West-Eberhard, 1989).
Meristic morphological characteristics, such as fin rays, gill rakers, and scale rows have historically served as an important method for identifying fish. Count data can be used in statistical analysis, allowing for comparison of populations and sexes (Barlow, 1961 cited in Begg and Waldman, 1999). Meristic characteristics vary within and among species, making them useful for describing or identifying fishes (Strauss and Bond, 1990). Morphometrics is the analysis of body shape and or shape of other morphological
zonatum Jordan, E. evergladei Jordan, E okefenokee Böhlke, E. bohlke Rohde and Arndt, E. okatie Rohde and Arndt, E. alabamae Mayden, and E. gilberti Snelson, Krabbenhoft and Quattro. Four of these seven species (E. alabamae, E. boehlkei, E. gilberti, and E. okatie) have only been described in the past 30 years (Rohde and Arndt 1987, Mayden 1993, Snelson et al. 2009). Five of the seven Elassoma species have restricted geographic distributions. Of these seven species, only the banded pygmy sunfish, Elassoma zonatum, occurs in Kentucky and was originally thought restricted to the coastal plain region (Clay, 1975). It is now known that E. zonatum populations in Kentucky inhabit three different drainages. The Coastal Plain population drains into the Mississippi and Tennessee rivers, while the Green River population drains into the