Red or yellow autumn leaves have long fascinated biologists, but their geographical concentration in trees in Eastern North America (ENA) has defied evolutionary explanations. In this review, ...anthocyanins and xanthophylls are discussed in relation to their occurrence in different regions of the Northern Hemisphere, phylogenetic distribution and photoprotective function during the breakdown of chlorophylls. Pigments in senescing leaves that intercept incident light and dissipate the absorbed energy extend the time available for nutrient resorption. Experiments with Arabidopsis have revealed greatest anthocyanin photoprotective function at low temperatures and high light intensities, and high-resolution solar irradiation maps reveal that ENA and Asia receive higher irradiation than does Europe. In addition, ENA experiences higher temperature fluctuations in autumn, resulting in cold snaps during leaf senescence. Under common garden conditions, chlorophyll degradation occurs earlier in ENA species than in their European and East Asian relatives. In combination, strong solar irradiation, temperature fluctuations and, on average, 3-wk shorter vegetation periods of ENA species favour investment in pigments to extend the time for nutrient resorption before abscission, explaining the higher frequency of coloured species in ENA compared to Europe. We end by outlining research that could test this new explanation of bright New England autumns.
Most extant genus-level radiations in gymnosperms are of Oligocene age or younger, reflecting widespread extinction during climate cooling at the Oligocene/Miocene boundary ∼23 million years ago ...(Ma). Recent biogeographic studies have revealed many instances of long-distance dispersal in gymnosperms as well as in angiosperms. Acting together, extinction and long-distance dispersal are likely to erase historical biogeographic signals. Notwithstanding this problem, we show that phylogenetic relationships in the gymnosperm family Cupressaceae (162 species, 32 genera) exhibit patterns expected from the Jurassic/Cretaceous breakup of Pangea. A phylogeny was generated for 122 representatives covering all genera, using up to 10,000 nucleotides of plastid, mitochondrial, and nuclear sequence per species. Relying on 16 fossil calibration points and three molecular dating methods, we show that Cupressaceae originated during the Triassic, when Pangea was intact. Vicariance between the two subfamilies, the Laurasian Cupressoideae and the Gondwanan Callitroideae, occurred around 153 Ma (124–183 Ma), when Gondwana and Laurasia were separating. Three further intercontinental disjunctions involving the Northern and Southern Hemisphere are coincidental with or immediately followed the breakup of Pangea.
• The family Araceae (3790 species, 117 genera) has one of the oldest fossil records among angiosperms. Ecologically, members of this family range from free‐floating aquatics (Pistia and Lemna) to ...tropical epiphytes. Here, we infer some of the macroevolutionary processes that have led to the worldwide range of this family and test how the inclusion of fossil (formerly occupied) geographical ranges affects biogeographical reconstructions. • Using a complete genus‐level phylogeny from plastid sequences and outgroups representing the 13 other Alismatales families, we estimate divergence times by applying different clock models and reconstruct range shifts under different models of past continental connectivity, with or without the incorporation of fossil locations. • Araceae began to diversify in the Early Cretaceous (when the breakup of Pangea was in its final stages), and all eight subfamilies existed before the K/T boundary. Early lineages persist in Laurasia, with several relatively recent entries into Africa, South America, South‐East Asia and Australia. • Water‐associated habitats appear to be ancestral in the family, and DNA substitution rates are especially high in free‐floating Araceae. Past distributions inferred when fossils are included differ in nontrivial ways from those without fossils. Our complete genus‐level time‐scale for the Araceae may prove to be useful for ecological and physiological studies.
Mutualisms that involve symbioses among specialized partners may be more stable than mutualisms among generalists, and theoretical models predict that in many mutualisms, partners exert reciprocal ...stabilizing selection on traits directly involved in the interaction. A corollary is that mutualism breakdown should increase morphological rates of evolution. We here use the largest ant-plant clade (Hydnophytinae), with different levels of specialization for mutualistic ant symbionts, to study the ecological context of mutualism breakdown and the response of a key symbiosis-related trait, domatium entrance hole size, which filters symbionts by size. Our analyses support three predictions from mutualism theory. First, all 12 losses apparently only occur from a generalist symbiotic state. Second, mutualism losses occurred where symbionts are scarce, in our system at high altitudes. Third, domatium entrance hole size barely changes in specialized symbiotic species, but evolves rapidly once symbiosis with ants has broken down, with a “morphorate map” revealing that hotspots of entrance hole evolution are clustered in high-altitude areas. Our study reveals that mutualistic strategy profoundly affects the pace of morphological change in traits involved in the interaction and suggests that shifts in partners’ relative abundances may frequently drive reversions of generalist mutualisms to autonomy.
The fossilized birth–death (FBD) model can make use of information contained in multiple fossils representing the same clade, and we here apply this model to infer divergence times in beeches (genus ...Fagus), using 53 fossils and nuclear sequences for all nine species. We also apply FBD dating to the fern clade Osmundaceae, with about 12 living species and 36 fossils. Fagus nuclear sequences cannot be aligned with those of other Fagaceae, and we therefore use Bayes factors to choose among alternative root positions. The crown group of Fagus is dated to 53 (62–43) Ma; divergence of the sole American species to 44 (51–39) Ma and divergence between Central European F. sylvatica and Eastern Mediterranean F. orientalis to 8.7 (20–1.8) Ma, unexpectedly old. The FBD model can accommodate fossils as sampled ancestors or as extinct or unobserved lineages; however, this makes its raw output, which shows all fossils on short or long branches, problematic to interpret. We use hand-drawn depictions and a bipartition network to illustrate the uncertain placements of fossils. Inferred speciation and extinction rates imply approximately 5× higher evolutionary turnover in Fagus than in Osmundaceae, fitting a hypothesized low turnover in plants adapted to low-nutrient conditions.
This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.
In contrast to most animals, plants have an indeterminate body plan, which allows them to add new body parts during their lifetime. A plant's realized modular construction is the result of exogenous ...constraints and endogenous processes. This review focuses on endogenous processes that shape plant architectures and their evolution.
The phylogenetic distribution of plant growth forms across the phylogeny implies that body architectures have originated and been lost repeatedly, being shaped by a limited set of genetic pathways. We (1) synthesize concepts of plant architecture, so far captured in 23 models; (2) extend them to the fossil record; (3) summarize what is known about their developmental genetics; (4) use a phylogenetic approach in several groups to infer how plant architecture has changed and by which intermediate steps; and (5) discuss which macroecological factors may constrain the geographic and ecological distribution of plant architectures.
Dichotomously branching Paleozoic plants already encompassed a considerable diversity of growth forms, here captured in 12 new architectural models. Plotting the frequency of branching types through time based on an analysis of 58 927 land plant fossils revealed a decrease in dichotomous branching throughout the Devonian and Carboniferous, mirrored by an increase in other branching types including axillary branching. We suggest that the evolution of seed plant megaphyllous leaves enabling axillary branching contributed to the demise of dichotomous architectures. The developmental-genetic bases for key architectural traits underlying sympodial vs. monopodial branching, rhythmic vs. continuous growth, and axillary branching and its localization are becoming well understood, while the molecular basis of dichotomous branching and plagiotropy remains elusive. Three phylogenetic case studies of architecture evolution in conifers, Aloe and monocaulous arborescent vascular plants reveal relationships between architectural models and show that some are labile in given groups, whereas others are widely conserved, apparently shaped by ecological factors, such as intercepted sunlight, temperature, humidity and seasonality.
Ribulose-1,5-Biphosphate-carboxylase-oxygenase (RuBisCO) has a crucial role in carbon fixation but a slow catalytic rate, a problem overcome in some plant lineages by physiological and anatomical ...traits that elevate carbon concentrations around the enzyme. Such carbon-concentrating mechanisms are hypothesized to have evolved during periods of low atmospheric CO ₂. Hornworts, the sister to vascular plants, have a carbon-concentrating mechanism that relies on pyrenoids, proteinaceous bodies mostly consisting of RuBisCO. We generated a phylogeny based on mitochondrial and plastid sequences for 36% of the approximately 200 hornwort species to infer the history of gains and losses of pyrenoids in this clade; we also used fossils and multiple dating approaches to generate a chronogram for the hornworts. The results imply five to six origins and an equal number of subsequent losses of pyrenoids in hornworts, with the oldest pyrenoid gained ca . 100 Mya, and most others at <35 Mya. The nonsynchronous appearance of pyrenoid-containing clades, the successful diversification of pyrenoid-lacking clades during periods with low CO ₂, and the maintenance of pyrenoids during episodes of high CO ₂ all argue against the previously proposed relationship between pyrenoid origin and low CO ₂. The selective advantages, and costs, of hornwort pyrenoids thus must relate to additional factors besides atmospheric CO ₂.
Aim
The field of biogeography is often described as a hub between research disciplines. Here we apply science mapping to study how biogeography has changed and evolved between 1995 and April 2022, ...and to analyse the mix of disciplines used in this field. We explore how research foci have changed over time and if biogeographical topics have entered the public discourse.
Location
Local to global.
Taxon
All taxa.
Methods
We created a semantic map of the field based on co‐occurrences of keywords or composite keywords from 40,000+ scientific papers published between the 1970s and April 2022, structuring these data into three hierarchical sets. A fourth set of Top 100 researchers was constructed in September 2022. To address our public‐discourse question, we used the Factiva archive of global media.
Results
Five core journals contained 14,386 papers (or 35.7% of the full set), while the remaining papers appeared in 2247 journals of which 59% included only one or two biogeographical papers. Since 1995, frequencies of keywords related to core concerns of biogeography have remained stable or even decreased, while ‘computing’ and ‘climate change’ have increased. There is an increasing association with Mathematics & Statistics, Computer Sciences, and Planning & Management, and a decreased association with Physical Geography. Biogeography‐related terms increasingly appearing in the public discourse are ‘biodiversity’, ‘urban nature’, ‘conservation’, ‘extinction’ and ‘rewilding’, while more technical concepts, such as ‘ecoregions’, ‘macroecology’ and ‘island biogeography’ remain at very low rates.
Main Conclusions
Biogeographical research is moving towards the social sciences, probably linked to a growing concern over global environmental issues and the Anthropocene. It is difficult to disentangle to what extent the public discourse is influenced by biogeographical research or vice versa, but ‘rewilding’ and ‘extinction’ are examples of topics that began in basic ecological‐biogeographical research and are now debated publicly.
Knowing the geographical origin of economically important plants is important for genetic improvement and conservation, but has been slowed by uneven geographical sampling where relatives occur in ...remote areas of difficult access. Less biased species sampling can be achieved when herbarium collections are included as DNA sources. Here, we address the history of Cucurbitaceae, one of the most economically important families of plants, using a multigene phylogeny for 114 of the 115 genera and 25 per cent of the 960 species. Worldwide sampling was achieved by using specimens from 30 herbaria. Results reveal an Asian origin of Cucurbitaceae in the Late Cretaceous, followed by the repeated spread of lineages into the African, American and Australian continents via transoceanic long-distance dispersal (LDD). North American cucurbits stem from at least seven range expansions of Central and South American lineages; Madagascar was colonized 13 times, always from Africa; Australia was reached 12 times, apparently always from Southeast Asia. Overall, Cucurbitaceae underwent at least 43 successful LDD events over the past 60 Myr, which would translate into an average of seven LDDs every 10 Myr. These and similar findings from other angiosperms stress the need for an increased tapping of museum collections to achieve extensive geographical sampling in plant phylogenetics.
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