Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
21,991
result(s) for
"Thomas, P. L."
Sort by:
A mega-phylogeny of the Annonaceae: taxonomic placement of five enigmatic genera and support for a new tribe, Phoenicantheae
The Annonaceae, the largest family in the early-divergent order Magnoliales, comprises 107 genera and c. 2,400 species. Previous molecular phylogenetic studies targeting different taxa have generated large quantities of partially overlapping DNA sequence data for many species, although a large-scale phylogeny based on the maximum number of representatives has never been reconstructed. We use a supermatrix of eight chloroplast markers (
rbcL
,
matK
,
ndhF
,
psbA-trnH
,
trnL-F
,
atpB-rbcL
,
trnS-G
and
ycf1
) to reconstruct the most comprehensive tree to date, including 705 species (29%) from 105 genera (98%). This provides novel insights into the relationships of five enigmatic genera (
Bocagea
,
Boutiquea
,
Cardiopetalum
,
Duckeanthus
and
Phoenicanthus
). Fifteen main clades are retrieved in subfamilies Annonoideae and Malmeoideae collectively, 14 of which correspond with currently recognised tribes.
Phoenicanthus
cannot be accommodated in any existing tribe, however: it is retrieved as sister to a clade comprising the tribes Dendrokingstonieae, Monocarpieae and Miliuseae, and we therefore validate a new tribe, Phoenicantheae. Our results provide strong support for many previously recognised groups, but also indicate non-monophyly of several genera (
Desmopsis
,
Friesodielsia
,
Klarobelia
,
Oxandra
,
Piptostigma
and
Stenanona
). The relationships of these non-monophyletic genera—and two other genera (
Froesiodendron
and
Melodorum
) not yet sampled—are discussed, with recommendations for future research.
Journal Article
Plant phylogeny as a window on the evolution of hyperdiversity in the tropical rainforest biome
Tropical rainforest (TRF) is the most species-rich terrestrial biome on Earth, harbouring just under half of the world’s plant species in c. 7% of the land surface. Phylogenetic trees provide important insights into mechanisms underpinning TRF hyperdiversity that are complementary to those obtained from the fossil record. Phylogenetic studies of TRF plant diversity have mainly focused on whether this biome is an evolutionary ‘cradle’ or ‘museum’, emphasizing speciation and extinction rates. However, other explanations, such as biome age, immigration and ecological limits, must also be considered. We present a conceptual framework for addressing the drivers of TRF diversity, and review plant studies that have tested them with phylogenetic data. Although surprisingly few in number, these studies point to old age of TRF, low extinction and high speciation rates as credible drivers of TRF hyperdiversity. There is less evidence for immigration and ecological limits, but these cannot be dismissed owing to the limited number of studies. Rapid methodological developments in DNA sequencing, macroevolutionary analysis and the integration of phylogenetics with other disciplines may improve our grasp of TRF hyperdiversity in the future. However, such advances are critically dependent on fundamental systematic research, yielding numerous, additional, well-sampled phylogenies of TRF lineages.
Journal Article
Origin and global diversification patterns of tropical rain forests: inferences from a complete genus-level phylogeny of palms
Background
Understanding how biodiversity is shaped through time is a fundamental question in biology. Even though tropical rain forests (TRF) represent the most diverse terrestrial biomes on the planet, the timing, location and mechanisms of their diversification remain poorly understood. Molecular phylogenies are valuable tools for exploring these issues, but to date most studies have focused only on recent time scales, which minimises their explanatory potential. In order to provide a long-term view of TRF diversification, we constructed the first complete genus-level dated phylogeny of a largely TRF-restricted plant family with a known history dating back to the Cretaceous. Palms (Arecaceae/Palmae) are one of the most characteristic and ecologically important components of TRF worldwide, and represent a model group for the investigation of TRF evolution.
Results
We provide evidence that diversification of extant lineages of palms started during the mid-Cretaceous period about 100 million years ago. Ancestral biome and area reconstructions for the whole family strongly support the hypothesis that palms diversified in a TRF-like environment at northern latitudes. Finally, our results suggest that palms conform to a constant diversification model (the 'museum' model or Yule process), at least until the Neogene, with no evidence for any change in diversification rates even through the Cretaceous/Paleogene mass extinction event.
Conclusions
Because palms are restricted to TRF and assuming biome conservatism over time, our results suggest the presence of a TRF-like biome in the mid-Cretaceous period of Laurasia, consistent with controversial fossil evidence of the earliest TRF. Throughout its history, the TRF biome is thought to have been highly dynamic and to have fluctuated greatly in extent, but it has persisted even during climatically unfavourable periods. This may have allowed old lineages to survive and contribute to the steady accumulation of diversity over time. In contrast to other plant studies, our results suggest that ancient and steady evolutionary processes dating back to the mid-Cretaceous period can contribute, at least in part, to present day species richness in TRF.
Journal Article
To adapt or go extinct? The fate of megafaunal palm fruits under past global change
Past global change may have forced animal-dispersed plants with megafaunal fruits to adapt or go extinct, but these processes have remained unexplored at broad spatio-temporal scales. Here, we combine phylogenetic, distributional and fruit size data for more than 2500 palm (Arecaceae) species in a time-slice diversification analysis to quantify how extinction and adaptation have changed over deep time. Our results indicate that extinction rates of palms with megafaunal fruits have increased in the New World since the onset of the Quaternary (2.6 million years ago). In contrast, Old World palms show a Quaternary increase in transition rates towards evolving small fruits from megafaunal fruits. We suggest that Quaternary climate oscillations and concurrent habitat fragmentation and defaunation of megafaunal frugivores in the New World have reduced seed dispersal distances and geographical ranges of palms with megafaunal fruits, resulting in their extinction. The increasing adaptation to smaller fruits in the Old World could reflect selection for seed dispersal by ocean-crossing frugivores (e.g. medium-sized birds and bats) to colonize Indo-Pacific islands against a background of Quaternary sea-level fluctuations. Our macro-evolutionary results suggest that megafaunal fruits are increasingly being lost from tropical ecosystems, either due to extinctions or by adapting to smaller fruit sizes.
Journal Article
Matching and Winning? The Impact of Upper and Middle Managers on Firm Performance in Major League Baseball
We investigate the joint impact of managers at different hierarchical levels on firm performance in Major League Baseball. We separately quantify the contribution of upper and middle managers and the impact of their
match quality
—the degree to which managers cooperate effectively across layers to impact firm success. We establish that match quality is a statistically significant and economically meaningful driver of firm performance. Higher-quality managers tend to be matched together across levels and achieve higher match quality during their joint employment. Match quality does not improve over the length of a joint employment spell, but lower match quality is found in pairs with more divergent educational attainment and prior strategic approaches. Hence, match quality is partly innate, and manager pairings may have difficulty improving their cooperation through learning. When we control for match quality, we find significantly lower estimates of heterogeneity in manager ability compared with commonly used estimators of managerial impact. Still, both middle and upper managers retain a meaningful impact on firm performance.
This paper was accepted by Bruno Cassiman, business strategy.
Journal Article