Biology subjects

Gamisch, A.

Publications and source records attributed to Gamisch, A..

3 recordsLinked to original sources

bioRxiv2021

Evolution of Crassulacean Acid Metabolism (CAM) as an escape from ecological niche conservatism in Malagasy Bulbophyllum (Orchidaceae)

Introductory paragraphDespite growing evidence that niche shifts are more common in flowering plants than previously thought, still little is known about the key physiological (e.g. photosynthesis) traits underlying such niche shifts. To address this question, we here combine a comprehensively sampled phylogeny for mostly epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope-derived photosynthesis data to infer the groups spatial-temporal history and to test the role of Crassulacean Acid Metabolism (CAM), a highly water-use efficient type of photosynthesis, in facilitating niche shifts and diversification. We find that most extant species still retain niche (Central Highland) and photosynthesis (C3) states as likely present in the single mid-Miocene (c. 12.70 Ma) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub-humid highland niche first into the islands humid eastern coastal, and then into the seasonally dry Northwest Sambirano rainforests, yet without significant effect on diversification rates. These findings support the rarely recognized hypothesis that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary gateway trait that considerably widened the spatial-ecological amplitude of Madagascars most species-rich orchid genus.

evolutionary biology↗

bioRxiv2020

Ambiguous support for extra-tropical accelerated diversification of rosids

Sun et al.1 used a comprehensive phylogenetic and a locality based climatic dataset to examine how past climates have driven diversification across 17 orders of rosids. They concluded that tropical rosids diversify slower than the (younger) non-tropical counterparts in part due to a strong negative relationship between paleo-temperature and diversification (i.e. higher diversification rates under lower temperatures). Their conclusions are based on tip rates (derived from BAMM2; DR3) and correlations with current temperature (e-SIM4) or binary tropicality data sets (BAMM/STRAPP5; FiSSE6) as well as tree-wide estimates of diversification with paleo-temperature (BAMM; RPANDA7) or tropicality (BiSSE8; HiSSE9). Here, I highlight several inconsistencies in their diversification analyses as well as a systematic error pertaining to the RPANDA model selection procedure, which, together with several minor technical issues, weaken the support for Sun et al.s1 conclusions. A re-analysis of their BiSSE/HiSSE and RPANDA analyses are performed.

evolutionary biology↗

bioRxiv2019

Genomic signature of shifts in selection in a sub-alpine ant and its physiological adaptations

Understanding how organisms adapt to extreme environments is fundamental and can provide insightful case studies for both evolutionary biology and climate-change biology. Here, we take advantage of the vast diversity of lifestyles in ants to identify genomic signatures of adaptation to extreme habitats such as high altitude. We hypothesised two parallel patterns would occur in a genome adapting to an extreme habitat: i) strong positive selection on genes related to adaptation and, ii) a relaxation of previous purifying selection. We tested this hypothesis by sequencing the high-elevation specialist Tetramorium alpestre and four other phylogenetic related species. In support of our hypothesis, we recorded a strong shift of selective forces in T. alpestre, in particular a stronger magnitude of diversifying and relaxed selection when compared to all other ants. We further disentangled candidate molecular adaptations in both gene expression and protein-coding sequence that were identified by our genome-wide analyses. In particular, we demonstrate that T. alpestre has i) a derived level of expression for stv and other heat-shock proteins in chill shock tests, and ii) enzymatic enhancement of Hex-T1, a rate-limiting regulatory enzyme that controls the entry of glucose into the glycolytic pathway. Together, our analyses highlight the adaptive molecular changes that support colonisation of high-altitude environments.

evolutionary biology↗