Uncommon Ground

Uncommon Ground

Tag Archive: Protea

The link between traits and performance in Protea

If you’re reading this, you probably know enough about me to know that my students and I have been working on Protea for the last 10-15 years. Today I am pleased to report that the most recent work, from Kristen Nolting’s PhD dissertation has appeared in Annals of Botany. The advance publication version appeared nearly a year ago, but the paper is officially out in a special issue focusing on intraspecific trait variation in plants. Here’s the abstract and a link.

Intraspecific trait variation influences physiological performance and fitness in the South Africa shrub genus Protea (Proteaceae)

Kristen M Nolting, Rachel Prunier, Guy F Midgley, Kent E Holsinger

Background and Aims

Global plant trait datasets commonly identify trait relationships that are interpreted to reflect fundamental trade-offs associated with plant strategies, but often these trait relationships are not identified when evaluating them at smaller taxonomic and spatial scales. In this study we evaluate trait relationships measured on individual plants for five widespread Protea species in South Africa to determine whether broad-scale patterns of structural trait (e.g. leaf area) and physiological trait (e.g. photosynthetic rates) relationships can be detected within natural populations, and if these traits are themselves related to plant fitness.

Methods

We evaluated the variance structure (i.e. the proportional intraspecific trait variation relative to among-species variation) for nine structural traits and six physiological traits measured in wild populations. We used a multivariate path model to evaluate the relationships between structural traits and physiological traits, and the relationship between these traits and plant size and reproductive effort.

Key Results

While intraspecific trait variation is relatively low for structural traits, it accounts for between 50 and 100 % of the variation in physiological traits. Furthermore, we identified few trait associations between any one structural trait and physiological trait, but multivariate regressions revealed clear associations between combinations of structural traits and physiological performance (R2 = 0.37–0.64), and almost all traits had detectable associations with plant fitness.

Conclusions

Intraspecific variation in structural traits leads to predictable differences in individual-level physiological performance in a multivariate framework, even though the relationship of any particular structural trait to physiological performance may be weak or undetectable. Furthermore, intraspecific variation in both structural and physiological traits leads to differences in plant size and fitness. These results demonstrate the importance of considering measurements of multivariate phenotypes on individual plants when evaluating trait relationships and how trait variation influences predictions of ecological and evolutionary outcomes.

Annals of Botany 127:519–531; 2021 https://doi.org/10.1093/aob/mcaa060

April 20, 2021 Botany, Ecology 0 Read more >

Trait-climate evolution in Protea

Protea compacta

If you’re reading this post, you know that my colleagues and I have been studying Protea for more than a decade. A lot of our work has focused on documenting and understanding trait-environment associations. We’ve studied those associations both among populations within species (Protea repens: https://doi.org/10.1093/aob/mcv146), among populations within a small, closely related clade (Protea sect. Exsertae: https://doi.org/10.1111/j.1558-5646.2010.01131.x and https://doi.org/10.1111/j.1420-9101.2012.02548.x), and across the entire genus (https://doi.org/10.1086/680051). But all of those studies look at the relationship between the climate as it is now (as reflected in the South African Atlas of Agrohydrology and Climatology). They haven’t examined how traits have evolved in response to changes in climate.

Our latest paper, begins to address that shortcoming. We use the highly resolved phylogeny of Protea that Nora Mitchell constructed as part of her dissertation (http://darwin.eeb.uconn.edu/uncommon-ground/blog/2017/01/23/a-new-phylogeny-for-protea/ and https://doi.org/10.3732/ajb.1600227), and we reconstruct estimates of how traits changed over evolutionary time in concert (or not) with climates. Our reconstructions depend on particular models of evolutionary change, and we explore several alternatives. Here’s the abstract:

Evolutionary radiations are responsible for much of Earth’s diversity, yet the causes of these radiations are often elusive. Determining the relative roles of adaptation and geographic isolation in diversification is vital to understanding the causes of any radiation, and whether a radiation may be labeled as “adaptive” or not. Across many groups of plants, trait–climate relationships suggest that traits are an important indicator of how plants adapt to different climates. In particular, analyses of plant functional traits in global databases suggest that there is an “economics spectrum” along which combinations of functional traits covary along a fast–slow continuum. We examine evolutionary associations among traits and between trait and climate variables on a strongly supported phylogeny in the iconic plant genus Protea to identify correlated evolution of functional traits and the climatic-niches that species occupy. Results indicate that trait diversification in Protea has climate associations along two axes of variation: correlated evolution of plant size with temperature and leaf investment with rainfall. Evidence suggests that traits and climatic-niches evolve in similar ways, although some of these associations are inconsistent with global patterns on a broader phylogenetic scale. When combined with previous experimental work suggesting that trait–climate associations are adaptive in Protea, the results presented here suggest that trait diversification in this radiation is adaptive.

Mitchell, N., J.E. Carlson, and K.E. Holsinger.  2018.  Correlated evolution between climate and suites of traits along a fast–slow continuum in the radiation of Protea. Ecology and Evolution 8:1853–1866. doi: 10.1002/ece3.3773.

February 7, 2018 Botany, Ecology 0 Read more >

Causes of genetic differentiation in Protea repens

American Journal of Botany Volume 104, Number 5. May 2017.

Protea repens is the most widespread member of the genus. It was one of the focal species in our recently completed Dimensions of Biodiversity project. Part of the project involved genotyping-by-sequencing analyses of 663 individuals from 19 populations spanning most of the geographical range of the species. We summarize results of those analyses in a paper that just appeared in advance of the May issue (cover photo featured above) of the American Journal of Botany. Here’s the abstract. You’ll find the citation and a link at the bottom.

PREMISE OF THE STUDY: The Cape Floristic Region (CFR) of South Africa is renowned for its botanical diversity, but the evolutionary origins of this diversity remain controversial. Both neutral and adaptive processes have been implicated in driving diversification, but population-level studies of plants in the CFR are rare. Here, we investigate the limits to gene flow and potential environmental drivers of selection in Protea repens L. (Proteaceae L.), a widespread CFR species.
METHODS: We sampled 19 populations across the range of P. repens and used genotyping by sequencing to identify 2066 polymorphic loci in 663 individuals. We used a Bayesian FST outlier analysis to identify single-nucleotide polymorphisms (SNPs) marking genomic regions that may be under selection; we used those SNPs to identify potential drivers of selection and excluded them from analyses of gene flow and genetic structure.
RESULTS: A pattern of isolation by distance suggested limited gene flow between nearby populations. The populations of P. repens fell naturally into two or three groupings, which corresponded to an east-west split. Differences in rainfall seasonality contributed to diversification in highly divergent loci, as do barriers to gene flow that have been identified in other species.
CONCLUSIONS: The strong pattern of isolation by distance is in contrast to the findings in the only other widespread species in the CFR that has been similarly studied, while the effects of rainfall seasonality are consistent with well-known patterns. Assessing the generality of these results will require investigations of other CFR species.

Prunier, R., M. Akman, C.T. Kremer, N. Aitken, A. Chuah, J. Borevitz, and K. E. Holsinger. Isolation by distance and isolation by environment contribute to population differentiation in Protea repens (Proteaceae L.), a widespread South African species. American Journal of Botany doi: 10.3732/ajb.1600232 

May 17, 2017 Botany, Population genetics 0 Read more >