Refine
Year of publication
- 2014 (3) (remove)
Document Type
- Doctoral Thesis (3) (remove)
Language
- English (3) (remove)
Has Fulltext
- yes (3)
Is part of the Bibliography
- no (3)
Institute
- Institut für Ökologie, Evolution und Diversität (3) (remove)
Panama is a megadiverse country that together with Costa Rica constitutes Lower Central America (LCA). Western Panama's Cordillera Central accounts for the eastern part of the LCA highlands shared between these countries. The aim of the present study is to compile the most complete and updated picture possible of the taxonomy, diversity, and distribution of reptiles that occur from 500 m asl upwards along the Talamanca and Tabasará ranges. These two continuous mountain ridges account for the western two-thirds of the Cordillera Central between the Costa Rican border and 81°W Including specimens collected four own research travels, I morphologically examined more than 1800 specimens, analyzed 16S and/or COI barcodes of 300 specimens, and performed a thorough search in literature and databases to obtain locality records for specimens and species occurrences. My complete occurrence dataset comprises 14620 georeferenced occurrence records in three quality categories. Conceivable occurrences of species not yet documented from a given area are evaluated on the basis of existing data either as "plausible" or "possible". I provide all datasets which I generated for this study in Appendices. The previously published descriptions of Dactyloa ginaelisae Lotzkat, Hertz, Bienentreu & Köhler 2013, Norops benedikti (Lotzkat, Bienentreu, Hertz & Köhler 2011), Sibon perissostichon Köhler, Lotzkat & Hertz 2010, and Sibon noalamina Lotzkat, Hertz & Köhler 2012 are included in the present work. In the course of integrative taxonomic analyses, I classify 15 genealogical lineages revealed by DNA barcoding within 7 anole species as Deep Conspecific Lineages (DCLs) because they lack consistent morphological differences to their nominal conspecifics. I provisionally classify 18 mitochondrial lineages found within six other anole species as Unconfirmed Genealogical Lineages (UGLs) pending adequate analyses of their morphological variation. I regard the two additional UGLs Celestus sp. and Geophis sp. and the two Confirmed Genealogical Lineages (CGLs) Lepidoblepharis sp. 1 and 2 to represent undescribed species. My taxonomic analyses yield the hitherto most comprehensive survey of the variability exhibited by dozens of reptile species in western Panama. The 16S and/or COI barcodes I provide represent 65 species recognized herein and constitute the first DNA barcode reference library for LCA reptiles. The reptile fauna of Panama comprises 265 species, including the four UGLs and CGLs mentioned above and characterized for the first time in this study, as well as Dendrophidion crybelum Cadle 2012 whose presence in the country I consider plausible. My occurrence dataset reveals that 160 of these species have been documented to occur in my study area. Adding the 20 species whose occurrence therein I consider plausible, I report the total species richness of the Talamanca and Tabasará ranges as comprising 180 species representing 81 genera in 25 families. With 178.8 species per 10 000 km2, the relative species richness of the area is extremely high even in a tropical context. In view of their overall documented distribution, I regard the presence of 27 additional species in my study area as possible. For the 180 species occurring in my study area I provide standardized species accounts that, together with the taxonomic results, for the first time permit the doubtless identification of all 180 species, and illustrate 168 of these with color photographs. Concerning biogeography, my georeferenced dataset yields noteworthy distribution extensions for many species. Moreover, I present the hitherto most comprehensive, detailed, and reproducible assessments of the distribution patterns, historical origins, and conservation as well as of the occurrence among physiographic regions, climatic and altitudinal belts, political subdivisions, and protected areas, for my study area's reptile fauna. With 65 species, more than a third of the fauna is endemic to LCA. Among these, 42 Talamancan highland endemics are restricted to the LCA highlands, in the case of 16 small-scale highland endemics with documented ranges spanning less than 100 km. I assess many of these endemics as endangered. The fact that several of these species do not occur in any protected area renders the establishment of additional conservation areas necessary, especially in the central Serranía de Tabasará. Distributional range boundaries shared among different clades of highland anoles indicate physiographic and climatic barriers that may have effected in situ speciation within these lineages. As the largest study on Panamanian reptile diversity assembled to date, the present dissertation considerably increases our knowledge on the reptiles along the Cordillera Central and beyond, and thus constitutes a solid basis for future studies.
Drought stress is one of the major abiotic factors diminishing crop productivity world wide. In the course of climate change, regions which already experience dry seasons nowadays will suffer from elongated drought periods and water shortage. These climatic changes will not only have an impact on the regional flora and fauna but also on the people inhabiting these areas. It is therefore of great importance to understand the reactions of plants to drought stress to help breeding and biotechnological approaches for the benefit of new robust cereal cultures growing under low water regimes. In this dissertation four grasses of the genus Panicum, P. bisulcatum (C3), P. laetum, P. miliaceum and P. turgidum (all C4 NAD-ME) were subjected to drought stress. The plants diverse reactions were investigated on a physiological as well as on a molecular level to deepen the understanding of drought stress responses. Drought stress was imposed for a species-specific period until a relative leaf water content (RWC) of ~50 % was reached in each grass. Physiological measurements were conducted on leaves with a RWC of ~50 % investigating chlorophyll a fluorescence parameters with a Plant Efficiency Analyzer (PEA) and gas exchange parameters like the photosynthesis rate and stomatal conductance with a Gas Fluorescence Chamber (GFS-3000). Subsequent molecular analysis were conducted on leaf samples taken (RWC = 50 %) analysing different proteins and the transcriptome of the Panicum species. The physiological measurements revealed a higher photosynthesis rate for the C4 grasses under drought stress with no significant differences between the C4 species. Also the water use efficiency was significantly higher in the C4 species in comparison to the C3 species independent from the water regime supporting results from the literature. The chlorophyll a measurements revealed the strongest adaptation to water shortage in the C4 species P. turgidum followed by the C3 species P. bisulcatum. It has been shown before (GHANNOUM 2009) that the C4 photosynthesis apparatus is more prone to drought stress than the C3 apparatus – despite the higher water use efficiency. Results also suggested that the great adaptation of P. turgidum to drought stress arose from its ability to recover from drought stress (all JIP test parameters showed no significant differences between control and recovery samples). The additional down-regulation of PS II but not of PS I under drought stress also helped the plant to endure times of water shortage and facilitated the recovery when water was available again. Protein analyses on the content of PEPC, OEC and RubisCO (LSU and SSU) revealed no changes. Dehydrin 1 in contrast was strongly up-regulated under drought stress and Summary 108 recovery in all four Panicum species. The stable content of the OEC protein was therefore not the catalyst of rising K peaks measured by chlorophyll a fluorescence and a reduced OEC activity was supposed. Transcriptomic analyses revealed a myriad of differentially regulated tags. Due to unsequenced genomes, tags could only be partially (8 % maximum for P. turgidum) annotated to their specific genes. Diverse methods were therefore used to annotate the most highly regulated tags to their genes and their products. Special emphasis was put on the regulation of five gene products confirming the regulation schemata from the HT-SuperSAGE analyses. Interestingly one protein – the NCED1 – was down-regulated under stress conditions, in contrast to results from the literature. It is therefore of great importance to investigate longer lasting drought to understand the full range of drought stress adaptation. Future genome sequencing projects might also include the Panicum species investigated in this dissertation and important gene candidates with no hits (maybe completely new to the research community) might help breeding and biotechnology approaches to produce more drought resistant crop species.
Understanding major causes of biodiversity and range dynamics requires research on evolutionary processes under consideration of environmental changes. In my thesis, I investigated the spatio-temporal evolution of the Neotropical tree genus Cedrela from the Meliaceae family by studying its genetic diversity, taxonomy, colonization history, climatic niche changes and dynamics of species distributions. My results show that climatic and geological changes are major drivers of biological diversification in Cedrela.