A century of Zoology and Entomology at Rhodes University, 1905 to 2005

The history of the Department of Zoology & Entomology at Rhodes University is traced from its origin with a single staff member, through the era of permanent heads of department to the present day staff. Significant achievements and developments in teaching and research are highlighted, and some anecdotal material is included

A Comparison and Combination of Plastid atpB and rbcL Gene Sequences for Inferring Phylogenetic Relationships within Orchidaceae

Parsimony analyses of DNA sequences from the plastid genes atpB and rbcL were completed for 173 species of Orchidaceae (representing 150 different genera) and nine genera from outgroup families in Asparagales. The atpB tree topology is similar to the rbcL tree, although the atpB data contain less homoplasy and provide greater jackknife support than rbcL alone. In combination, the two-gene tree recovers five monophyletic clades corresponding to subfamilies within Orchidaceae, and fully resolves them with moderate to high jackknife support as follows: Epidendroideae are sister to Orchidoideae, followed by Cypripedioideae, then Vanilloideae, and with Apostasioideae sister to the entire family. Although this two-gene hypothesis of orchid phylogeny is an improvement over all single-gene studies published to date, there is still no consensus as to how all the tribes of Epidendroideae are related to one another. Nevertheless, these new topologies help to clarify some of the anomalous results recovered when rbcL was previously analyzed alone, and demonstrate the value of continued plastid gene sequencing within Orchidaceae

Across the Apocalypse on Horseback: Imperfect Legal Responses to Biodiversity Loss

Life on Earth overcomes mass extinction events on a temporal scale spanning millions of years. By this measure, “the loss of genetic and species diversity” is probably the contemporary crisis “our descendants [will] most regret” and “are least likely to forgive.” Biodiversity loss is the “scientific problem of greate[st] immediate importance for humanity.” If indeed biodiversity loss has reached apocalyptic proportions, it is fitting to describe the engines of extinction in equine terms. Jared Diamond characterizes the deadly horsemen of the ecological apocalypse as an “Evil Quartet” consisting of habitat destruction, overkill, introduced species, and secondary extinctions. Edward O. Wilson prefers an acronym derived from the Greek word for horse. HIPPO represents Habitat destruction, Invasive species, Pollution, Population, and Overharvesting. Although conservation biologists have identified the leading causes of biodiversity loss, legal responses to the crisis do not address distinct sources of human influence on evolutionary change. Not surprisingly, legal scholarship tends to ignore the distinctions among causes of biodiversity loss. This Essay takes a modest step toward remedying at least the latter shortcoming

Pollination and evolution of the genus Mystacidium (Orchidaceae)

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.The morphology, anatomy and pollination biology of Mystacidium Lindl., a small, epiphytic genus of orchids, was investigated within a phylogenetic context. Morphological and anatomical studies were carried out in order to obtain characters for a cladistic analysis of the genus using Cyrtorchis arcuata (Lindl.) Schltr. as an outgroup. The phylogenetic analysis indicated that the genus may not be monophyletic. Two species of the closely related genus Diaphananthe Schltr., D. caffra (H.Bol.) Linder and D. millarii (H.Bol.) Linder, appear to be nested within Mystacidium. Mystacidium species grow in habitats varying from mistbelt forest to dry savanna. Analysis of stable isotope composition (Ȣ¹³C values) of leaves and roots showed that all Mystacidium species, as well as D. caffra and the outgroup C. arcuata, employ CAM photosynthesis. The Ȣ¹³C values were significantly negatively correlated with mean annual rainfall at the collection sites. Breeding system experiments revealed that Mystacidium is dependent on pollinators for fruit set, and that self-pollination results in substantially reduced seed set due to either inbreeding depression or partial self-incompatibility. Field observations revealed that M. venosum Harv. ex Rolfe and M. capense (L.f.) Schltr. are hawkmoth-pollinated, and that M. gracile Harv. and M. pusillum Harv. are pollinated by settling moths. The spurs of the flowers contain dilute, sucrose-dominant nectar. Mystacidium venosum and M. capense showed evidence of nectar reabsorption. Nocturnal emission of scent occurred in all species except M. aliceae H. Bolus and M. brayboniae Summerh., which are unscented, and was composed largely of a combination of monoterpenes and benzoids. Despite substantial variation in spur length (1 - 4.7 cm) among species, no evidence for directional selection on spur length was found in M. venosum, M. capense or M. gracile. Hand pollinations significantly increased fruit set in M. capense in two consecutive seasons at different sites, indicating pollen limitation. Although pollen removal was greater than pollen receipt in M. venosum, M. capense and M. gracile, suggesting transport loss or insufficient visitation, a remarkably high percentage of removed pqllen reached stigmas (35 - 50%). Experiments on M. venosum revealed that flower longevity is reduced by pollination, and that pollinia removed from flowers remained viable for up to 20 days under field conditions. The phylogeny indicated that long-spurred, hawkmoth-pollinated species are basal within the genus, and that shorter-spurred species pollinated by noctuid moths are derived

Nectar Theft and Floral Ant-Repellence: A Link between Nectar Volume and Ant-Repellent Traits?

As flower visitors, ants rarely benefit a plant. They are poor pollinators, and can also disrupt pollination by deterring other flower visitors, or by stealing nectar. Some plant species therefore possess floral ant-repelling traits. But why do particular species have such traits when others do not? In a dry forest in Costa Rica, of 49 plant species around a third were ant-repellent at very close proximity to a common generalist ant species, usually via repellent pollen. Repellence was positively correlated with the presence of large nectar volumes. Repellent traits affected ant species differently, some influencing the behaviour of just a few species and others producing more generalised ant-repellence. Our results suggest that ant-repellent floral traits may often not be pleiotropic, but instead could have been selected for as a defence against ant thieves in plant species that invest in large volumes of nectar. This conclusion highlights to the importance of research into the cost of nectar production in future studies into ant-flower interactions

Concordance of genetic variation that increases risk for anxiety disorders and posttraumatic stress disorders and that influences their underlying neurocircuitry

Background There have been considerable recent advances in understanding the genetic architecture of anxiety disorders and posttraumatic stress disorder (PTSD), as well as the underlying neurocircuitry of these disorders. However, there is little work on the concordance of genetic variations that increase risk for these conditions, and that influence subcortical brain structures. We undertook a genome-wide investigation of the overlap between the genetic influences from single nucleotide polymorphisms (SNPs) on volumes of subcortical brain structures and genetic risk for anxiety disorders and PTSD. Method We obtained summary statistics of genome-wide association studies (GWAS) of anxiety disorders (Ncases=?7016, Ncontrols=?14,745), PTSD (European sample; Ncases=?2424, Ncontrols=?7113) and of subcortical brain structures (N?=?13,171). SNP Effect Concordance Analysis (SECA) and Linkage Disequilibrium (LD) Score Regression were used to examine genetic pleiotropy, concordance, and genome-wide correlations respectively. SECAs conditional false discovery was used to identify specific risk variants associated with anxiety disorders or PTSD when conditioning on brain related traits. Results For anxiety disorders, we found evidence of significant concordance between increased anxiety risk variants and variants associated with smaller amygdala volume. Further, by conditioning on brain volume GWAS, we identified novel variants that associate with smaller brain volumes and increase risk for disorders: rs56242606 was found to increase risk for anxiety disorders, while two variants (rs6470292 and rs683250) increase risk for PTSD, when conditioning on the GWAS of putamen volume. Limitations Despite using the largest available GWAS summary statistics, the analyses were limited by sample size. Conclusions These preliminary data indicate that there is genome wide concordance between genetic risk factors for anxiety disorders and those for smaller amygdala volume, which is consistent with research that supports the involvement of the amygdala in anxiety disorders. It is notable that a genetic variant that contributes to both reduced putamen volume and PTSD plays a key role in the glutamatergic system. Further work with GWAS summary statistics from larger samples, and a more extensive look at the genetics underlying brain circuits, is needed to fully delineate the genetic architecture of these disorders and their underlying neurocircuitry

Filogenia molecular de las orquídeas del género Dracula en el Ecuador, utilizando ITS como marcador molecular.

El objetivo fue establecer la filogenia molecular de las orquídeas del género Dracula en el Ecuador, utilizando el Espaciador Transcrito Interno (ITS) como marcador molecular; para lo cual se recolectaron 54 de las 55 especies descritas en el país en un total de 108 muestras de coleccionistas y orquidearios ubicados en las provincias de Carchi y Pichincha. El análisis molecular se efectuó para abordar problemas de clasificación de este género e híbridos artificiales confundidos como nuevas especies, la extracción de ADN se lo hizo mediante el protocolo químico de Doyle & Doyle, posteriormente se amplificaron las muestras con el marcador molecular ITS1 para la cadena Fordware e ITS4 para la cadena Reverse, en electroforesis horizontal mediante la técnica de Reacción en cadena de polimerasa (PCR) convencional para su posterior secuenciación en Macrogen. La generación de cladogramas se trabajó con el software MEGA 7. Se tomaron dos especies del género Masdevallia y la especie Diodonopsis erinacea como grupos externos para el enraizamiento del árbol. La utilización del marcador ITS nos deja más claro el entender la evolución del género y de varias especies dentro de él, la formación de clados y la ausencia de híbridos, sin embargo, ya que es un marcador universal puede generar errores en los cladogramas los cuales exhibieron varias secciones de rama subdivididas y al ser este el primer estudio que aplica ITS en este tipo de orquídeas, no se puede comparar resultados con cladogramas definidos por este marcador. Se recomienda investigar nuevas regiones de ADN cloroplástico y nuclear para poder resolver la controversia que presenta la clasificación desactualizada del género.The objetive was to stablish the molecular phylogeny of the Dracula orchids kind in Ecuador, by using the Internal Trascribed Spacer (ITS) as a molecular marker; for which it has been recollect 54 or 55 species described in the country in a total of 108 samples from collectors and orchidariums located in the Carchi and Pichincha province. The molecular analysis was made to avoid any classification problems for these gender and artificial hybrids confuse with new species, the extraction of the DNA was made by a chemical protocol of Doyle & Doyle, subsequently the molecular marker samples the ITS1 for the Fordware chain and the ITS4 for the reverse chain were amplified, in horizontal electrophoresis through the polymerase chain reaction technique (PCR) conventional for its further sequencing in Macrogen, the generation of cladograms ware made with the MEGA 7 software. Two kind of species were taken, the Masdevallia and Diodopnosis erinacea species as external groups for rooting the tree. The used of the marker ITS leave a more clear understanding of the evolution of this gender and many others species inside of it, the formation of clades and the absence of hybrids, despite this, as a universal marker it could generate mistakes on the cladograms the ones that show many sections of subdivided ranges and to be this the first study to apply the ITS on these type of orchids, the results cannot be compare with the defined cladograms by this marker. Its recommend to investigate new regions of chloroplastic and nuclear DNA to resolve the controversy that presents the outdated classification of the gender