Adept at Adapting: Response to climate change in flowering and migration phenology

Spicebush (Lindera benzoin) flowers in mid-April at Manitoga, Garrison, NY

“The observed and predicted changes in plant distribution and phenology have major implications for various ecological and evolutionary phenomena, including ecosystem productivity, species interactions, community structure, and conservation of biodiversity.” (1)

In my blog post postulating that native plants could be our canary in the coal mine for conditions inhospitable for humans, I suggested it is not a good thing for humans to evolve adaptions to survive excessive heat, drought, and pollution of air and water. Evidence shows, however, that adaptation is exactly what at least some plants and animals need in order to live through global climate change.

Multiple taxa in MA, for example, have advanced in flowering 4 days for every degree centigrade rise in spring (1). In some cases this has amounted to a few weeks earlier. Thanks to Henry David Thoreau, there are data from his writings on the phenology of flowering plants in Concord, MA 150 years ago. Matched to contemporary data, there is evidence that species shifting their first-flowering time in sync with earlier warming dates have seen an increase in abundance. Introduced species, and especially those known now as invasive, have been better able to adapt their response to warming (2). Plants that have not made that shift have decreased in abundance or disappeared from the flora of Concord, including asters, dogwoods, lilies, roses and violets (3,4).

The evolutionary biologists studying this see possibilities for predicting ecological fitness: if one tracks the phenological response to change of a plant, then its relatives from the earliest common ancestor (or clade) is likely to have the same response (4). The examples they cite are the families of Asteraceae, Iridaceae and Orchidaceae as being particularly unsuited to adjusting their phenology.  This is very bad news for the fynbos of South Africa, which has an extremely rich flora, but at least 25% of it is composed of species from these three families (5).

Why is this happening? There is probably more than one factor—one certainly being that plants depending on sexual reproduction, as opposed to vegetative, have co-evolved with their pollinators and seed dispersers.  Changes that affect one will have implications for the other. A plant that flowers 2-3 weeks earlier than usual may not be visited by the specialized insect that it needs for pollination, unless the pollinator or disperser has made the shift as well. It is apparently typical that in a given area plants and their pollinators and herbivores adapt to temperature changes at different rates (1). Bertin also describes lower elevation plants in Europe increasing their ranges upward, since in the Italian Alps, for example, the warming trend decreases frost damage and increases the growing season with earlier snowmelt. This may not actually be beneficial for the plants if their essential pollinators do not make the ascent. It is definitely not beneficial for skiers.

A bee is in sync with the flowering of pussywillow in Loveland, OR. Photo credit with permission: Ejel Stonesifer.

Phenology is also a limiting factor for migrating birds. Accounting for other variables like degraded winter habitat, birds that do not advance their migration phenology to arrive coincident with earlier life cycles of the food-source plants or insects are most at risk for declining populations. These are the insectivorous, forest-breeding, long-distance migratory passerines—certain warblers and flycatchers, and finches, for example (4, 6). Birds that can take advantage of the earlier and/or shorter food peaks (residents and short-distance migrants, such as swans, pigeons, and gulls) do not suffer similar declines (4, 7).

Habitats with short bursts of food supply will have specialist foragers, both animals and insects, who will suffer decline as the window of food availability shortens. Plants with a narrow ecological niche that depends on synchronicity with specialist pollinators and seed dispersers have suffered decline. “Biological change begets more biological change…the emergence of trees created a diverse new set of niches that formerly did not exist” (8). Evolution to new floral or reproductive characteristics in response to pollinators is possible, but in some cases this will no doubt take more time than the increasingly rapid changes in climate will allow (9).

I referred to disappearing or novel climates in my most recent post. Our past biological history may serve us poorly for predictions of the future. For the near future, perhaps we should say it looks as if climate change will favor generalist species of all taxonomic kingdoms– those with wide ecological amplitude and more than one way to reproduce.

References:

1. Bertin, R.I. (2008) Plant phenology and distribution in relation to recent climate change.  Journal of the Torrey Botanical Society, 135(1): 126-146.

2. Willis, C.G., et al (2010) Favorable climate change response explains non-native species’ success in Thoreau’s woods.  PLoS ONE 5(1): e8878. doi:10.1371/journal.pone.ooo8878 (This is an open access journal, freely available online)

3.  Willis, C.G, et al (2008) Phylogenetic patterns of species loss in Thoreau’s woods are driven by climate change. Proceedings of the National Academy of Sciences, 105(44): 17029-17033.

4. Davis, C.C., C.G. Willis, R.B. Primack, A.J. Miller-Rushing (2010) The importance of phylogeny to the study of phenological response to global climate change. Philosophical Transactions of the Royal Society B, 365: 3201-3213. (A free-access journal, with issues available online one year after publication).

5. Davis, C.C., E.J. Edwards, M.J. Donoghue (2010) A clade’s eye view of global climate change. In Evolution Since Darwin: The first 150 years: pp. 623-627.  Pub. by Sinauer Associates, Inc., Sunderland, MA.

6. Moller, A.P., D. Rubolini, E. Lehikoinen (2008) Populations of migratory bird species that did not show a phenological response to climate change are declining. Proceedings of the National Academy of Sciences, 105(42): 16195-16200.

7. Both, C., et al (2010) Avian population consequences of climate change are most severe for long-distance migrants in seasonal habitats. Proceedings of the Royal Society B, 277: 1259-1266.  (All Proceedings B content is free to access between 1 and 10 years after publication)

8. Beckage, B., L.J. Gross, S. Kauffman. (2011) The limits to prediction in ecological systems. Ecosphere 2(11): 125. doi:10.1890/ ES11-00211.1. (An open access article found thru Google Scholar)

9. Campbell, D.R. (2008) Pollinator shifts and the origin and loss of plant species. Annals of the Missouri Botanical Garden 95(2): 264-274. (Available thru the JSTOR database, which can be accessed at many academic libraries)

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