Ecophenotypic variation

Abstract: Taxonomic concepts of Early–Middle Cenomanian representatives of Schloenbachia Neumayr, 1875 are evaluated based on well-preserved, abundant faunas from NE Iran (Atamir Formation, Koppeh Dagh) and Germany (Essen Greensand and Baddeckenstedt formations at several localities in northern Germany; Meisen Formation of Saxony). From a single Lower Cenomanian horizon in the Atamir Formation, a complete suite of specimens of Schloenbachia varians (J. Sowerby, 1817), ranging from moderately involute, compressed and finely ornamented (“forma subplana”) to more evolute, depressed and strongly spinose forms (“forma ventriosa”) with all transitional morphologies, is documented. Also in the shallow-water faunas of the “Klippenfazies” of the Essen Greensand Formation at Mulheim-Broich and of the Meisen Formation, all morphotypes co-occur. Thus, these forms cannot be regarded as geographic subspecies or successive chrono-subspecies, but reflect a high degree of variability in shell form and ornament (phenotypic plasticity) in S. varians. Interestingly, strongly tuberculate forms are rare to absent in contemporaneous offshore settings as documented by the Baddeckenstedt Formation. The phenotypic plasticity in Early Cenomanian S. varians populations is explained by ecophenotypic variation along a depth (proximal–distal) gradient: strongly tuberculate, depressed forms reflect comparatively shallow, nearshore environments with higher water energy and predation pressure, whereas compressed, weakly ornamented morphs are forms of open (and deeper) marine waters. The complete range of different forms is also observed in micro- and macroconchs, suggesting that the morphological variability is not controlled by sexual dimorphism. Based on its similarity to S. varians, also the Middle Cenomanian Ammonites coupei Brongniart, 1822 may be placed in the synonymy of the former.

Abstract: Geomorphological methods for quantifying branching networks are used to describe inter- and intra-specific differences in branching patterns among two species of arborescent Caribbean gorgonian, Plexaura homomalla, P. flexuosa, and a third, undescribed plexaurid from the San Blas Islands, Panama. There were significant differences among species for first, second and third order branch lengths, and for tributary to source ratios for first and second order branches. Extrapolations from the branching parameters successfully predicted differences in the branch structure of naturally generated colony fragments. Within P. homomalla, significant differences with depth in the lengths and tributary to source ratios of first, second, and third order branches provide a measure of the greater bushiness of shallow water colonies. These measures can be used to quantify morphological differences in both ecological and systematic analyses. Data on the branching characters of these three gorgonian species demonstrate that gross colony form can be studied as a quantifiable component of phenotype and that gorgonians display both species level and ecophenotypic variation in colony form.

Abstract: Clavelina lepadiformis is a colonial ascidian found in harbour and rocky littoral habitats. The populations of these 2 habitat types in the Western Mediterranean showed marked genetic dif- ferences in mtDNA sequence data in previous works. However, no morphological differences between the forms inhabiting the 2 habitat types have been found. Here, we compared the biology and accu- mulation of heavy metals in populations of both habitats in NE of Spain. Abundance and seasonal cycles showed contrasting trends in the 2 habitat types: harbour populations reached densities of ca. 3900 zooids m -2 and active colonies were found all year round. Abundance in the rocky littoral environment was 1 order of magnitude lower and showed a clear seasonal pattern, with the disap- pearance of zooids during summer (aestivation). Reproductive cycles also differed, as larvae were pre- sent in the harbour population from November through June, with several sexual cycles during this period. In contrast, in the open littoral, larval occurrence was restricted to 2 to 3 mo during winter- spring, with only 1 gonadal cycle yr -1 . The zooids and larvae of the harbour were significantly larger. However, neither the total reproductive effort, tunic production (in weight ratios) nor fecundity signif- icantly differed between these habitats. The harbour population accumulated significantly more Cu and Pb, and heavy metal concentrations showed a seasonal cycle with minima in summer. On the other hand, both populations accumulated a similar amount of V, a metal involved in ascidian metabolism. The production of secondary metabolites and the toxicity of polar extracts were higher in the open lit- toral form. These results, however, did not correlate with the outcome of palatability tests carried out with specialist and generalist predators, in which no preference was observed. Experimental juvenile transplantation between habitats showed that newly settled individuals from the rocky littoral habitat can survive in both environments (with survival rates of 30 to 50% during the first 4 wk), while those from harbours show low survivorship when moved out (ca. 5% survival after 4 wk). We conclude that there was a marked ecophenotypic variation between populations of both habitat types.