Similar forces of selection operating on multiple taxa can cause convergent evolution of quantitative traits. When those same forces of selection occur across an environmental gradient a phenotypic cline may evolve. I have conducted an experiment in central Texas to test whether seed oil melting points and proportions of saturated fatty acids have repeatedly evolved to germinate as predicted by theory. Species with lower seed oil melting points and proportions of saturated fatty acids are expected to germinate at cooler temperatures than ones that germinate at warmer temperatures. Field observations were conducted at two sites for one year to characterize germination temperatures of sixteen species. Gas chromatography was utilized to describe the fatty acid compositions and melting points of those species’ triacylglycerol (oil) stores. The field sites produced conflicting results. At one site, all analyses supported the theory. Whereas evidence from the other site either contradicted expectation or was equivocal. Likewise there was some evidence that plants with annual life histories are under stronger selection to evolve melting points that approximate germination temperature than species with perennial life histories. Finally, evidence was found that a higher level of variation in seed oil melting point and percent of saturated fatty acids is maintained in species that were observed to germinate at low temperatures relative to species observed to germinate at higher temperatures. / text

New Zealand's five endemic mudfish (Neochanna spp.) species have distributions that differ both geographically and by habitat type. Differences in habitat preferences between species have led to the proposal of an evolutionary series within the group. A morphological cline can be observed from the galaxiform Chatham Island and Canterbury species inhabiting lakes and streams, respectively, to the anguilliform Northland and brown mudfishes of ephemeral wetlands. Morphological specializations proposed for wetland dwelling include loss of pelvic fins, reduced eyes, enlarged nostrils, development of caudal flanges, and elongation of dorsal and anal fin bases to become almost confluent with the caudal fin. Another expectation of adaptation to wetland dwelling is specializations in respiratory physiology to obtain oxygen from highly hypoxic or acidic waters, and the ability to cope with seasonal exposure to air during the drought season. Expected respiratory specializations to wetland dwelling include high oxygen affinity haemoglobins, high levels of cooperative oxygen binding, the presence of multiple haemoglobins and the ability to aestivate and survive long periods of emersion. The four mainland Neochanna species were examined to determine if differences in haemoglobin expression as well as differences in haemoglobin oxygen binding correlated with differing habitats and treatments. Whole blood oxygen affinity was determined at several pH levels (6.5, 7.0, 7.5 and 8.0) and temperatures (10'C, 15'C and 20'C), as well as different treatments (aestivating, fasting and control) using a Hemox analyzer. The presence of multiple haemoglobins was determined by isoelectric focusing. All four species displayed high oxygen affinities (p50 = 6.5 to 9.5 mm Hg at pH 7.5 15'C), moderate levels of cooperativity (Hill coefficients = 1.75 to 2.00 at pH 7.5 15'C), pH sensitivity (Bohr coefficients = -0.62 to -0.94 between pH 7.5 and 7.0 at 15'C), temperature sensitivity (ΔH = -2.20 to -15.78 k cal mol-1 between 10'C and 15'C) and the presence of multiple haemoglobins. Black, brown and Northland mudfish were able to survive aestivation for six weeks but there were no changes between air-breathing and water-breathing individuals with respect to oxygen binding characteristics. Although there is evidence of habitat specialization in haemoglobin physiology between mudfish species, differences between species did not correlate with the evolutionary series proposed for specialization to dwelling in ephemeral wetlands and latitudinal distributions of mudfish species appear to strongly dictate oxygen binding properties of mudfish whole blood.