Peter Stafford

Low levels of nucleotide diversity in Crocodylus moreletii and evidence of hybridization with C. acutus

Examinations of both population genetic structure and the processes that lead to such structure in crocodilians have been initiated in several species in response to a call by the IUCN Crocodile Specialist Group. A recent study used microsatellite markers to characterize Morelets crocodile (Crocodylus moreletii) populations in north-central Belize and presented evidence for isolation by distance. To further investigate this hypothesis, we sequenced a portion of the mitochondrial control region for representative animals after including samples from additional locales in Belize, Guatemala and Mexico. While there is limited evidence of subdivision involving other locales, we found that most of the differentiation among populations of C. moreletiican be attributed to animals collected from a single locale in Belize, Banana Bank Lagoon. Furthermore, mitochondrial DNA sequence analysis showed that animals from this and certain other locales display a haplotype characteristic of the American crocodile, C. acutus, rather than C. moreletii. We interpret this as evidence of hybridization between the two species and comment on how these new data have influenced our interpretation of previous findings. We also find very low levels of nucleotide diversity in C. moreletiihaplotypes and provide evidence for a low rate of substitution in the crocodilian mitochondrial control region. Finally, the conservation implications of these findings are discussed.

Palynology and systematics of Ranunculiflorae

The pollen morphological variation in the families of the Ranunculiflorae (Berberidaceae, Fumariaceae, Lardizabalaceae Menispermaceae Nelumbonaceae, Papaveraceae and Ranunculaceae) is summarised and discussed in relation to the systematics of the group. The pollen grains are generally dispersed as monads, but permanent tetrads occur in a few instances. Aperture numbers range from one, in spiraperturate pollen of Berberis and some species of Anemone and in the rare monosulcate grains that occur in some individuals of Nelumbo, to three in the majority of species, to many. These tricolpate-derived forms range from zonocolpate to pantocolpate and pantoporate forms. With the exception of some Papaver species, the occurrence of endoapertures appears restricted to Menispermaceae, where they are generally present. The ornamentation is generally punctate to microreticulate, often with spinules or striate to striate-reticulate. The exine stratification is generally tectate-columellate, with a granular infratectum in some taxa, and the endexine is well developed. Pollen grains of Ranunculiflorae exhibit successiformy and spiralization, two of the evolutionary patterns that were first recognised and defined by Van Campo (1967, 1976). These pollen morphological patterns result in a high level of homoplasy (similarity arising through convergent or parallel evolution). Many of the palynological characters are autapomorphic and thus serve to identify distinctive taxa (such as Berberis or Fumaria). Fewer characters can clearly be recognised as synapomorphies at the familial or subfamilial level, especially in the absence of a detailed character analysis integrating palynological and other kinds of evidence. One potentially important character that may not be subject to extensive homoplasy is the occurrence of a compound layer of striae (sensu Nowicke & Skvarla 1982) in contrast to psilate, punctate or microreticulate ornamentation with scabrae or microechinae.

Pollen morphology of the genus Pelargonium (Geraniaceae)

Abstract The pollen grains from a selection of species representing each of the recognised sections of Pelaronium and covering the geographical range of the genus were studied with a view to compiling keys and descriptions for their identification in the scanning electron microscope and compound light microscope. The pollen was examined and separated into pollen types representing the lowest recognisable taxonomic units on the basis of pollen morphological characteristics, principally exine structure and ornamentation. The greater majority of species were found to fall into a general striate/reticulate ornamentation type within which it was not possible to distinguish between species, although a number of other pollen types and subgroups could be identified by differences in their reticulum and ornamentation. The palynological results are discussed with respect to current systematic treatments of Pelargonium .

Aperture variation in the pollen of Nelumbo (Nelumbonaceae)

The evolutionary and developmental origin of tricolpate pollen is of great interest because pollen of this kind defines a major clade of angiosperms (eudicots), a clade that is also well supported by molecular data. We examined evidence that tricolpate and monosulcate pollen types are produced alongside each other in the anthers of Nelumbo flowers, as has previously been reported. Observations of pollen in situ within individual anthers revealed mainly tricolpate pollen produced in tetrahedral tetrads, but also a small percentage of clearly aberrant pollen grains that have a great variety of aperture configurations. Previously published evidence for tetragonal tetrads is not supported, and previously reported monosulcate grains are part of a continuum of variation among the aberrant grains in aperture number, position and form. Other eudicots show similar variability in their pollen apertures. The variation in the pollen of Nelumbo is not exceptional, and may not be more significant than variation seen in the other taxa with regard to the origin of the tricolpate and tricolpate‐derived pollen characteristic of eudicots. Nevertheless further studies of aberrant pollen in Nelumbo and other eudicots, together with comparisons of pollen development in “normal” eudicots and closely related species that show radical, and developmentally fixed, reorganization of apertures and pollen polarity, may be helpful in understanding the processes that controlled the transition from the monosulcate to the tricolpate condition.

Pollen morphology and systematics of the zygomorphic‐flowered nightshades (Solanaceae; Salpiglossideae sensu D'Arcy, 1978 and Cestroideae sensu D'Arcy, 1991, pro parte): A review

Abstract Pollen morphology was studied in 72 species and 20 genera of the zygomorphic‐flowered Solanaceae (tribe Salpiglossideae as traditionally defined, the ‘basal’ nightshades), inclusive of their putative relatives. Results are compared with two markedly different current treatments of taxonomic relationships within this heterogenous group. Fifteen principal pollen types are recognised based on grain size, shape, aperture type, features of sculpturing, exine stratification and dispersal mode. Pollen grains may be 3–7 zonocolpate to colporate and oblate‐prolate, with polar axis measurements ranging from 15 μm to more than 60 μm. In most taxa the exine is characterised by a reticulate ornamentation pattern, but in others it is rugulate, striate, punctate or micoechinate. Tetrahedral tetrads (acalymmate) were observed in species of four genera ‐ Bouchetia, Nierembergia, Reyesia and Salpiglossis ‐ with the walls of adjacent monads linked by direct exinal bridges. Palynological evidence does not appear to support present generic limits, and a preliminary set of taxonomically and potentially phylogenetically useful pollen characters is presented.

Diet and reproductive ecology of the Yucatán cricket-eating snake Symphimus mayae (Colubridae)

Measurement and dissection of 97 museum specimens provided information on morphology, food habits, and reproduction in the colubrid snake Symphimus mayae. This medium-sized ( 50% of the total number of prey items recovered from stomachs and had been eaten by > 70% of the snakes examined, with little intraspecific or seasonal variation. Other, less frequently used prey groups are (in order of relative importance), stick insects, mantids, Jerusalem crickets, grasshoppers and spiders. All size classes of snakes eat orthopterans, but stick insects are consumed predominantly by adults (> 300 mm SVL), and mantids exclusively by large adults (> 420mm SVL). More than 55% of individuals from monthly samples contained recently ingested food, suggesting that feeding in S. mayae occurs year-round and is not significantly curtailed by the local dry season. Reproduction is probably annual, although it does not occur in all females every year, and a single clutch of two to four eggs is produced with oviposition and hatching timed to the wet season.