| 1. |
- Abrahamczyk, S., et al.
(författare)
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Pollinator adaptation and the evolution of floral nectar sugar composition
- 2017
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 30:1, s. 112-127
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Tidskriftsartikel (refereegranskat)abstract
- A long-standing debate concerns whether nectar sugar composition evolves as an adaptation to pollinator dietary requirements or whether it is 'phylogenetically constrained'. Here, we use a modelling approach to evaluate the hypothesis that nectar sucrose proportion (NSP) is an adaptation to pollinators. We analyse similar to 2100 species of asterids, spanning several plant families and pollinator groups (PGs), and show that the hypothesis of adaptation cannot be rejected: NSP evolves towards two optimal values, high NSP for specialist-pollinated and low NSP for generalist-pollinated plants. However, the inferred adaptive process is weak, suggesting that adaptation to PG only provides a partial explanation for how nectar evolves. Additional factors are therefore needed to fully explain nectar evolution, and we suggest that future studies might incorporate floral shape and size and the abiotic environment into the analytical framework. Further, we show that NSP and PG evolution are correlated - in a manner dictated by pollinator behaviour. This contrasts with the view that a plant necessarily has to adapt its nectar composition to ensure pollination but rather suggests that pollinators adapt their foraging behaviour or dietary requirements to the nectar sugar composition presented by the plants. Finally, we document unexpectedly sucrose-poor nectar in some specialized nectarivorous bird-pollinated plants from the Old World, which might represent an overlooked form of pollinator deception. Thus, our broad study provides several new insights into how nectar evolves and we conclude by discussing why maintaining the conceptual dichotomy between adaptation and constraint might be unhelpful for advancing this field.
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| 2. |
- Bolinder, Kristina, et al.
(författare)
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From near extinction to diversification by means of ashift in pollination mechanism in the gymnosperm relict Ephedra (Ephedraceae, Gnetales)
- 2016
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Ingår i: Botanical journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4074 .- 1095-8339. ; 180:4, s. 461-477
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Tidskriftsartikel (refereegranskat)abstract
- Pollination in gymnosperms is usually accomplished by means of wind, but some groups are insect-pollinated. We show that wind and insect pollination occur in the morphologically uniform genus Ephedra (Gnetales). Based on field experiments over several years, we demonstrate distinct differences between two Ephedra species that grow in sympatry in Greece in pollen dispersal and clump formation, insect visitations and embryo formation when insects are denied access to cones. Ephedra distachya, nested in the core clade of Ephedra, is anemophilous, which is probably the prevailing state in Ephedra. Ephedra foeminea, sister to the remaining species of the genus, is entomophilous and pollinated by a range of diurnal and nocturnal insects. The generalist entomophilous system of E.foeminea, with distinct but infrequent insect visitations, is in many respects similar to that reported for Gnetum and Welwitschia and appears ancestral in Gnetales. The Ephedra lineage is well documented already from the Early Cretaceous, but the diversity declined dramatically during the Late Cretaceous, possibly to near extinction around the Cretaceous-Palaeogene boundary. The clade imbalance between insect- and wind-pollinated lineages is larger than expected by chance and the shift in pollination mode may explain why Ephedra escaped extinction and began to diversify again.
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| 3. |
- Bolinder, Kristina, et al.
(författare)
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Pollen morphology of Ephedra (Gnetales) and its evolutionary implications
- 2016
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Ingår i: Grana. - : Informa UK Limited. - 0017-3134 .- 1651-2049. ; 55:1, s. 24-51
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Tidskriftsartikel (refereegranskat)abstract
- The Ephedra lineage can be traced at least to the Early Cretaceous. Its characteristically polyplicate pollen is well-represented in the fossil record and is frequently used as an indicator of paleoclimate. However, despite previous efforts, knowledge about variation and evolution of ephedroid pollen traits is poor. Here, we document pollen morphology of nearly all extant species of Ephedra, using a combination of scanning electron microscopy (SEM) and light microscopy (LM), and reconstruct ancestral states of key pollen traits. Our results indicate that the ancestral Ephedra pollen type has numerous plicae interspaced by unbranched pseudosulci, while the derived pollen type has branched pseudosulci and (generally) fewer plicae. The derived type is inferred to have evolved independently twice, once along the North American stem branch and once along the Asian stem branch. Pollen of the ancestral type is common in Mesozoic fossil records, especially from the Early Cretaceous, but it is less commonly reported from the Cenozoic. The earliest documentation of the derived pollen type is from the latest Cretaceous, after which it increases strongly in abundance during the Paleogene. The results of the present study have implications for the age of crown group Ephedra as well as for understanding evolution of pollination syndromes in the genus.
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| 4. |
- Garwood, Nancy C., et al.
(författare)
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Trema domingensis rises like a phoenix from the ashes of Trema integerrima : A reassessment of the entire-leaved species of Neotropical Trema (Cannabaceae)
- 2018
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Ingår i: Journal of the Botanical Research Institute of Texas. - : Botanical Research Institute of Texas. - 1934-5259 .- 2644-1608. ; 12:2, s. 555-577
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Tidskriftsartikel (refereegranskat)abstract
- We resolve three problems concerning the three entire-leaved species of Neotropical Trema. 1) Phylogenetic and morphological results showed that T. integerrima (Beurl.) Standl., T. domingensis Urb., and T. laxiflora Lundell are a single species; therefore, we combine them under a single name. 2) The date of publication gives priority to T. integerrima, as the basionym Sponia integerrima Beurl. was published in 1856. However, the type specimen, Billberg 308 (S), is not a species of Trema but Pouzolzia obliqua (Wedd.) Wedd. (Urticaceae); therefore, Sponia integerrima Beurl. is a new synonym of P. obliqua. The next available name for the entire-leaved species is T. domingensis, published in1912. 3) The type of T. domingensis, Fuertes 312, is a mixed collection. Specimens of Fuertes 312 held at B, NY, U, and USD are T. domingensis, while those at P, G, US, and Z are Celtis trinervia Lam. We provide a historical review to understand how these problems arose and persisted unnoticed for decades.
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| 5. |
- Humphreys, Aelys M., et al.
(författare)
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Detecting evolutionarily significant units above the species level using the generalised mixed Yule coalescent method
- 2016
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Ingår i: Methods in Ecology and Evolution. - 2041-210X. ; 7:11, s. 1366-1375
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Tidskriftsartikel (refereegranskat)abstract
- There is renewed interest in inferring evolutionary history by modelling diversification rates using phylogenies. Understanding the performance of the methods used under different scenarios is essential for assessing empirical results. Recently, we introduced a new approach for analysing broadscale diversity patterns, using the generalised mixed Yule coalescent (GMYC) method to test for the existence of evolutionarily significant units above the species (higher ESUs). This approach focuses on identifying clades as well as estimating rates, and we refer to it as clade-dependent. However, the ability of the GMYC to detect the phylogenetic signature of higher ESUs has not been fully explored, nor has it been placed in the context of other, clade-independent approaches. We simulated >32000 trees under two clade-independent models: constant-rate birth-death (CRBD) and variable-rate birth-death (VRBD), using parameter estimates from nine empirical trees and more general parameter values. The simulated trees were used to evaluate scenarios under which GMYC might incorrectly detect the presence of higher ESUs. The GMYC null model was rejected at a high rate on CRBD-simulated trees. This would lead to spurious inference of higher ESUs. However, the support for the GMYC model was significantly greater in most of the empirical clades than expected under a CRBD process. Simulations with empirically derived parameter values could therefore be used to exclude CRBD as an explanation for diversification patterns. In contrast, a VRBD process could not be ruled out as an alternative explanation for the apparent signature of hESUs in the empirical clades, based on the GMYC method alone. Other metrics of tree shape, however, differed notably between the empirical and VRBD-simulated trees. These metrics could be used in future to distinguish clade-dependent and clade-independent models. In conclusion, detection of higher ESUs using the GMYC is robust against some clade-independent models, as long as simulations are used to evaluate these alternatives, but not against others. The differences between clade-dependent and clade-independent processes are biologically interesting, but most current models focus on the latter. We advocate more research into clade-dependent models for broad diversity patterns.
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| 6. |
- Puglielli, Giacomo, et al.
(författare)
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Abiotic stress tolerance can explain range size and filling in temperate woody plants
- 2023
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Ingår i: Perspectives in plant ecology, evolution and systematics. - 1433-8319 .- 1618-0437. ; 59
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Tidskriftsartikel (refereegranskat)abstract
- Efforts to understand the mechanisms explaining the relationship between abiotic stress tolerance and range size and filling have hitherto yielded contradictory results. Unlike previous studies that have focused on single stress factors, we here examine the extent to which range size and filling can be explained by tolerance of multiple abiotic stressors (cold, shade, drought and waterlogging). As range metrics, we used range size and filling (the ratio between actual and potential range) for 331 European and North American temperate woody plant species. Stress tolerance strategies were expressed as a multivariate axis reflecting a cold/waterlogging-drought tolerance trade-off. We used mixed models to evaluate the relationship between range size/filling and this multivariate stress tolerance axis, using latitude as a covariate, and phylogeny and plant functional type as random effects. Range size and stress tolerance were negatively correlated, mostly independently of latitude and continent. Thus, cold/wet-tolerant species had the largest range sizes and cold-sensitive/drought-tolerant species the smallest. In contrast, range filling mostly depended on latitude. Our results show that abiotic stress tolerance can explain interspecific differences in range size, and to a lesser extent range filling, which sets up predictions for range size variation in plants that go beyond latitude.
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| 7. |
- Abrahamczyk, Stefan, et al.
(författare)
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Evolution of brood-site mimicry in Madagascan Impatiens (Balsaminaceae)
- 2021
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Ingår i: Perspectives in plant ecology, evolution and systematics. - : Elsevier BV. - 1433-8319 .- 1618-0437. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- The species-rich flora of Madagascar is well known for a range of unusual floral ecologies. One example is Impatiens section Trimorphopetalum with its unique combination of floral traits: small, spur-less, cup-or lip shaped, greenish or brownish flowers. So far no hypotheses on floral function or pollination of this peculiar group have been proposed. We analysed six reproductive traits in relation to pollination syndromes for 34 Madagascan Impatiens species, including 18 species of section Trimorphopetalum plus six outgroup species, in a phylogenetic framework. Further, we present pollinator observations for one additional species of Trimophopetalum. All pollination syndromes occurring in the African species are also present in Madagascan Impatiens. In addition, species of Trimorphopetalum represent two unique floral types, possibly corresponding to two different types of fly pollination. The evolution of these flower types corresponds to a strong decrease in nectar production, flower display size, pollen grain and ovule number. Autogamy is found in one derived sub-clade of the otherwise largely pollinator-dependent Trimorphopetalum. We find evidence consistent with the evolution of brood-site deception and fungus mimicry in combination with fly pollination in one clade of Trimorphopetalum and the stepwise evolution of autogamy in the second clade. The evolution of these very different reproductive strategies may have been triggered by pollinator limitation in the dense, humid forest undergrowth of Madagascar.
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| 8. |
- Barraclough, Timothy G., et al.
(författare)
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The evolutionary reality of species and higher taxa in plants : a survey of post-modern opinion and evidence
- 2015
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 207:2, s. 291-296
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Forskningsöversikt (refereegranskat)abstract
- Species are normally considered to be the fundamental unit for understanding the evolution of biodiversity. Yet, in a survey of botanists in 1940, twice as many felt that plant genera were more natural units than plant species. Revisiting the survey, we found more people now regarded species as a more evolutionarily real unit, but a sizeable number still felt that genera were more evolutionarily real than species. Definitions of evolutionarily real' split into those based on shared evolutionary history and those based on shared evolutionary fate via ongoing evolutionary processes. We discuss recent work testing for shared evolutionary fate at the species and higher levels and present preliminary evidence for evolutionarily significant higher taxa in plants.
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| 9. |
- Cousins-Westerberg, Ruben, et al.
(författare)
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Evolution of cold tolerance in the highly stress-tolerant samphires and relatives (Salicornieae: Amaranthaceae) : Amaranthaceae)
- 2023
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Ingår i: Botanical journal of the Linnean Society. - 0024-4074 .- 1095-8339. ; 203:1, s. 20-36
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Tidskriftsartikel (refereegranskat)abstract
- Low temperature constitutes one of the main barriers to plant distributions, confining many clades to their ancestrally tropical biome. However, recent evidence suggests that transitions from tropical to temperate biomes may be more frequent than previously thought. Here, we study the evolution of cold and frost tolerance in the globally distributed and highly stress-tolerant Salicornieae (Salicornioideae, Amaranthaceae s.l.). We first generate a phylogenetic tree comprising almost all known species (85-90%), using newly generated (n = 106) and published nuclear-ribosomal and plastid sequences. Next, we use geographical occurrence data to document in which clades and geographical regions cold-tolerant species occur and reconstruct how cold tolerance evolved. Finally, we test for correlated evolution between frost tolerance and the annual life form. We find that frost tolerance has evolved independently in up to four Northern Hemisphere lineages but that annuals are no more likely to evolve frost tolerance than perennials, indicating the presence of different strategies for adapting to cold environments. Our findings add to mounting evidence for multiple independent out-of-the-tropics transitions among close relatives of flowering plants and raise new questions about the ecological and physiological mechanism(s) of adaptation to low temperatures in Salicornieae.
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| 10. |
- Hjertaas, Ane C., et al.
(författare)
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Convergent evolution of the annual life history syndrome from perennial ancestors
- 2023
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 13
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Forskningsöversikt (refereegranskat)abstract
- Despite most angiosperms being perennial, once-flowering annuals have evolved multiple times independently, making life history traits among the most labile trait syndromes in flowering plants. Much research has focused on discerning the adaptive forces driving the evolution of annual species, and in pinpointing traits that distinguish them from perennials. By contrast, little is known about how ‘annual traits’ evolve, and whether the same traits and genes have evolved in parallel to affect independent origins of the annual syndrome. Here, we review what is known about the distribution of annuals in both phylogenetic and environmental space and assess the evidence for parallel evolution of annuality through similar physiological, developmental, and/or genetic mechanisms. We then use temperate grasses as a case study for modeling the evolution of annuality and suggest future directions for understanding annual-perennial transitions in other groups of plants. Understanding how convergent life history traits evolve can help predict species responses to climate change and allows transfer of knowledge between model and agriculturally important species.
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