| 1. |
- Joffard, Nina, et al.
(author)
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Extensive pollinator sharing does not promote character displacement in two orchid congeners
- 2022
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In: Evolution. - : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 76:4, s. 749-764
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Journal article (peer-reviewed)abstract
- Pollinator sharing between close relatives can be costly and can promote pollination niche partitioning and floral divergence. This should be reflected by a higher species divergence in sympatry than in allopatry. We tested this hypothesis in two orchid congeners with overlapping distributions and flowering times. We characterized floral traits and pollination niches and quantified pollen limitation in 15 pure and mixed populations, and we measured phenotypic selection on floral traits and performed controlled crosses in one mixed site. Most floral traits differed between species, yet pollinator sharing was extensive. Only the timing of scent emission diverged more in mixed sites than in pure sites, and this was not mirrored by the timing of pollinator visitation. We did not detect divergent selection on floral traits. Seed production was pollen limited in most populations but not more severely in mixed sites than in pure sites. Interspecific crosses produced the same or a higher proportion of viable seeds than intraspecific crosses. The two orchid species attract the same pollinator species despite showing divergent floral traits. However, this does not promote character displacement, implying a low cost of pollinator sharing. Our results highlight the importance of characterizing both traits and ecological niches in character displacement studies.
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| 2. |
- Opedal, Øystein H., et al.
(author)
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Measuring, comparing and interpreting phenotypic selection on floral scent
- 2022
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In: Journal of evolutionary biology. - : Wiley. - 1010-061X .- 1420-9101. ; 35:11, s. 1432-1441
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Journal article (peer-reviewed)abstract
- Natural selection on floral scent composition is a key element of the hypothesis that pollinators and other floral visitors drive scent evolution. The measure of such selection is complicated by the high-dimensional nature of floral scent data and uncertainty about the cognitive processes involved in scent-mediated communication. We use dimension reduction through reduced-rank regression to jointly estimate a scent composite trait under selection and the strength of selection acting on this trait. To assess and compare variation in selection on scent across species, time and space, we reanalyse 22 datasets on six species from four previous studies. The results agreed qualitatively with previous analyses in terms of identifying populations and scent compounds subject to stronger selection but also allowed us to evaluate and compare the strength of selection on scent across studies. Doing so revealed that selection on floral scent was highly variable, and overall about as common and as strong as selection on other phenotypic traits involved in pollinator attraction or pollen transfer. These results are consistent with an important role of floral scent in pollinator attraction. Our approach should be useful for further studies of plant–animal communication and for studies of selection on other high-dimensional phenotypes. In particular, our approach will be useful for studies of pollinator-mediated selection on complex scent blends comprising many volatiles, and when no prior information on the physiological responses of pollinators to scent compounds is available.
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| 3. |
- Sletvold, Nina, et al.
(author)
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Fine-scale genetic structure in the orchid Gymnadenia conopsea is not associated with density of flowering plants
- 2024
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In: American Journal of Botany. - : John Wiley & Sons. - 0002-9122 .- 1537-2197. ; 111:2
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Journal article (peer-reviewed)abstract
- Premise: Density-dependent pollinator visitation can lead to density-dependent mating patterns and within-population genetic structure. In Gymnadenia conopsea, individuals in low-density patches receive more self pollen than individuals in high-density patches, suggesting higher relatedness at low density. Ongoing fragmentation is also expected to cause more local matings, potentially leading to biparental inbreeding depression.Methods: To evaluate whether relatedness decreases with local density, we analyzed 1315 SNP loci in 113 individuals within two large populations. We quantified within-population genetic structure in one of the populations, recorded potential habitat barriers, and visualized gene flow using estimated effective migration surfaces (EEMS). We further estimated the magnitude of biparental inbreeding depression that would result from matings restricted to within 5 m.Results: There was no significant relationship between local density and relatedness in any population. We detected significant fine-scale genetic structure consistent with isolation by distance, with positive kinship coefficients at distances below 10 m. Kinship coefficients were low, and predicted biparental inbreeding depression resulting from matings within the closest 5 m was a modest 1–3%. The EEMS suggested that rocks and bushes may act as barriers to gene flow within a population.Conclusions: The results suggest that increased self-pollen deposition in sparse patches does not necessarily cause higher selfing rates or that inbreeding depression results in low establishment success of inbred individuals. The modest relatedness suggests that biparental inbreeding depression is unlikely to be an immediate problem following fragmentation of large populations. The results further indicate that habitat structure may contribute to governing fine-scale genetic structure in G. conopsea.
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| 4. |
- Söderquist, Linus, et al.
(author)
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Genetic structure and diversity of the declining orchid Gymnadenia conopsea in Scandinavia: implications for conservation and management
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Other publication (other academic/artistic)abstract
- Understanding how historical versus contemporary processes shape population genetic structure and variation is important to design effective management actions for threatened species. To unravel population structure, connectivity, and genetic variation in the declining Gymnadenia conopsea, we genotyped 1,834 SNPs in 1,120 individuals in 110 populations, in three different habitats (fen, meadow, coastal) across Scandinavia. We further tested if genetic diversity increases with census population size, and is higher in core habitats (fen and meadow) than in marginal, coastal habitats. We identified three main genetic clusters and pronounced isolation by distance, consistent with two independent colonization routes after last glacial maximum, followed by admixture. Estimates of effective migration using EEMS indicated reduced gene flow between coastal and inland populations, suggesting that the complex topography of the fjord landscape constitutes a dispersal barrier. Genetic diversity increased with census population size. The highest genetic diversity was found in core habitats, in meadows in southern Sweden and in inland fens along the Scandes mountains, while the lowest genetic diversity was found on the Atlantic coast and in a few populations scattered across Scandinavia. Genetic diversity did not vary significantly among habitat types. In conclusion, current genetic structure suggests a strong legacy of historical events, and the high genetic diversity documented in the main Scandinavian range indicates that both current viability and future adaptation potential is high. To maintain genetic diversity and connectivity, it is particularly important to preserve southern meadow populations, which depend on traditional land use, along with central fen populations.
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| 5. |
- Joffard, Nina, et al.
(author)
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Digest : The role of postzygotic isolation in Mimulus speciation
- 2021
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In: Evolution: international journal of organic evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 75:3, s. 756-758
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Journal article (peer-reviewed)abstract
- Recently diverged species often show incomplete reproductive isolation and subsequently experience hybridization and introgression. The plant genus Mimulus includes many such examples of closely related taxa that prove useful for studying incipient speciation. However, Sandstedt et al. show that in contrast to other Mimulus species, species of the M. tilingii complex are characterized by strong postzygotic isolation mediated by multiple barriers. This finding highlights the diverse speciation histories of related plant groups.
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| 6. |
- Joffard, Nina, et al.
(author)
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Floral trait differentiation in Anacamptis coriophora : Phenotypic selection on scents, but not on colour
- 2020
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In: Journal of Evolutionary Biology. - : WILEY. - 1010-061X .- 1420-9101. ; 33:8, s. 1028-1038
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Journal article (peer-reviewed)abstract
- Current divergent selection may promote floral trait differentiation among conspecific populations in flowering plants. However, whether this applies to complex traits such as colour or scents has been little studied, even though these traits often vary within species. In this study, we compared floral colour and odour as well as selective pressures imposed upon these traits among seven populations belonging to three subspecies of the widespread, generalist orchidAnacamptis coriophora. Colour was characterized using calibrated photographs, and scents were sampled using dynamic headspace extraction and analysed using gas chromatography-mass spectrometry. We then quantified phenotypic selection exerted on these traits by regressing fruit set values on floral trait values. We showed that the three studied subspecies were characterized by different floral colour and odour, with one of the two predominant floral volatiles emitted by each subspecies being taxon-specific. Plant size was positively correlated with fruit set in most populations, whereas we found no apparent link between floral colour and female reproductive success. We detected positive selection on several taxon-specific compounds inA. coriophorasubsp. fragrans, whereas no selection was found on floral volatiles ofA. coriophorasubsp. coriophoraandA. coriophorasubsp.martrinii. This study is one of the first to document variation in phenotypic selection exerted on floral scents among conspecific populations. Our results suggest that selection could contribute to ongoing chemical divergence amongA. coriophorasubspecies.
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| 7. |
- Schatz, Bertrand, et al.
(author)
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Is Ophrys pollination more opportunistic than previously thought? : Insights from different field methods of pollinator observation
- 2021
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In: BOTANY LETTERS. - : Taylor & Francis. - 2381-8107 .- 2381-8115. ; 168:3, s. 333-347
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Journal article (peer-reviewed)abstract
- Global changes induce a general decline in the abundance and diversity of European orchids and their pollinators. Such a decline is especially likely to affect species engaged in specialized interactions, thereby causing their replacement by generalists. In this study, we focused on sexually deceptive orchids from the genus Ophrys, which are often described as extreme specialists. We describe several observations of Ophrys pollinators in the Mediterranean region in order to: i) compare four different field methods to monitor Ophrys pollinators, and ii) provide more information on these pollinators to re-evaluate the specialization of Ophrys-pollinator interactions and discuss the ecological context in which these interactions take place. We discovered several new pollinator species for various Ophrys taxa, including unexpected ones. We also showed that the prolonged observation of mass-flowering and neighbouring Ophrys plants optimizes the chances of observing Ophrys pollinators without disturbing natural pollination. We argue that Ophrys pollination may be more opportunistic than classically described in the literature, likely involving one main pollinator and one or several secondary pollinators across the range of each Ophrys species. This study provides new methodological and conceptual insights into Ophrys pollination.
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