Preamble
Be honest now. How often does a cross-building collaboration
between two grad students get launched? Our paper, now available on early view
in TREE, is the result of a couple PhD students from different departments at
UBC learning through the grapevine that they were thinking about the same idea:
recent evolutionary processes that lead to ecosystem services. Seth (Zoology)
already had a manuscript when Maayan (Resources, Environment, and
Sustainability) heard about him through a mutual friend and they joined forces.
We both had a remarkably similar take on the idea that rapid evolution could
generate not just costs, but also services that benefit people. Though writing
a paper that’s accessible for both conservation scientists and evolutionary
biologists was a bit challenging, we had good representation of the two ‘sides’
between the two of us (as well as Kai and Dolph) so the battles were balanced
and we ended up understanding more about each other’s disciplinary quirks and
anxieties: Maayan now knows the fine differences between evolutionary and
genetic rescue; Seth knows never to conflate ecosystem service supply with
benefit. After 15 months of deciding on examples, wrangling terms, and creating
and destroying framing categories, the paper is done, and it’s pretty much what
we had in mind: an ‘idea’ piece squarely aimed at both conservation scientists
and evolutionary ecologists exploring how sometimes rapidly evolving species
can benefit people.
The authors benefitting from eco- and evo-system
services. Clockwise from top left: Seth Rudman holding a beautiful and delicious Lake Michigan Lake Trout
(Salvelinus namaycush), the abundance
of which may have been buoyed by character displacement between alewife and
bloater chub. Maayan Kreitzman picking an apple that was probably not too badly infested with the Apple
Maggot (Rhagoletis pommonella) due to
the cascading speciation of R. pomonella
predators. Dolph Schluter clearly enjoying the sense of place imparted
by getting close to squirrel
monkeys on the Amazon River near Leticia, Colombia. Kai Chan glowing from the cultural
and social cohesion generated with his daughter while kayaking on Campbell Lake
near Parry Sound, Ontario.
Eco-evolutionary
dynamics and people
Rapid evolution can alter ecological process, but how best
to quantify this alteration? Previous
work has used measures of the effect size of intraspecific variation on the abundances
of interacting species, metrics of community composition, and measures of
ecosystem functions (a fantastic early example is [1]). Yet, as biologists who are keenly aware of
the goods and services that nature provides for human health and well-being,
perhaps measuring or calculating the contribution of rapid evolution to
ecosystem services is more informative in some cases. The ecosystem services concept links the
functioning of ecosystems and the material or nonmaterial benefits that humans
derive from them. (As such, ecosystem services is an unabashedly
anthropocentric concept - though not necessarily an exclusively materialistic
one. So when we talk about benefits and costs, we’re doing so in the ecosystem
services context, ie from a human perspective, not from the perspective of
other species.) By assessing the way that rapid evolutionary change alters
ecosystem services we could focus our efforts on measuring how evolution alters
the components of communities and ecosystems we humans rely upon the most,
thereby translating the importance of rapid evolution into units often used for
conservation and management decisions.
In our TREE paper (freshly available on early view [2]), we hope to provide a
foundation for such work by providing a framework for rapid evolution and
ecosystem services, and describing some promising examples.
We have long known that rapid evolution can cause powerful
negative impacts: antibiotic resistance and pesticide resistance are two
classic areas of applied evolutionary biology.
However, there have not been attempts to document when rapid evolution
might enhance ecosystem services. To
this end, we define the term contemporary
evosystem services as “the maintenance or increase of an ecosystem service
resulting from evolution occurring quickly enough to alter ecological
processes”. This term, and our opinion
manuscript as a whole, owes quite a bit to previous work on evosystem services [3,4], which first
recognized the role that evolution can play in ecosystem services.
A history of the term
‘evosystem services’
This previous work, while it recognized the potentially
beneficial role of rapid evolution, had a different focus and orientation: the
aim of Faith et al. 2010 and Hendry et al. 2010 was to use the increasingly
popular language of ecosystem services to draw attention to the importance of
preserving biodiversity. In our initial submission we roundly criticized this
term as being too meta-scale to be informative and we considered repurposing
the term evosystem services to refer only to the contemporary contribution of
evolution to ecosystem services. We came to our sense when we paid greater
attention to the history of the term. In
part, this was due to the interesting history the proprietor of this blog
(Andrew Hendry) shared with us on his
review for TREE of our second submission (reproduced with permission and a few
small tweaks by Hendry, emphasis ours):
A brief history of the
term evosystem services might be interesting to the authors, reviewers, and
editor. I am not saying this history needs to be added to the paper. The idea
came from concerns among evolutionary biologists involved in international
biodiversity NGOs (DIVERSITAS, FUTURE EARTH, IPBES) that the justification of
biodiversity conservation by reference to ecosystem services (the major trend
in such NGOs) ran the risk of preserving only the few perceived
"useful" components of biodiversity, rather than biodiversity per se.
A group of us (including Faith) involved in these NGOs were concerned that
evolutionary components of biodiversity were
no longer of primary conservation concern, nor was rapid evolution being
considered. Over discussions, we realized that ecosystem services were, in
reality, a good justification for considering evolution per se once one
recognized that ecosystem services were the product of evolution in the past,
present, and future. Hence, the Faith definition as quoted in this MS was
originally intended specifically to make evosystem services synonymous with
ecosystem services - to make clear the importance of studying evolutionary
diversity even when interested in ecosystem services. [A Hendry 4/9/2017: Stated more correctly, ecosystem services ARE evosystem services.] Thus, the original intent of the term was exactly that which authors of
the present MS criticize - that it is all inclusive and, as the authors argue,
therefore unhelpful). Personally, I am fine with the authors’ redefinition
of the term to focus on contemporary evolution with ecological impacts (rapid
evolution) on ecosystem services, but I think they should at least be aware
that the original all-inclusiveness of the term was intentionally a strategic
attempt to increase attention paid to evolutionary patterns and processes when
using ecosystem services as justification for biodiversity conservation. It
might be valuable for the authors to at least point out that they are not
questioning the importance of past evolution for ecosystem services - and that
this link is an important point to recognize in biodiversity science (cite
Faith). It is just that the present MS is focusing on the contemporary
"rapid" aspect of this idea.
As we can see, the term evosystem
services was originally meant to stress the inclusion of thinking about
evolutionary diversity in conservation circles, and to mitigate against the
idea that all of nature is appropriate fodder for tinkering and management,
which the ecosystem services concept might seem to encourage. As stated above,
Faith and Hendry et al. were arguing that all ecosystem services are evosystem services because past,
present, and future evolution is at the root of all possible ecosystem
services. While this is undoubtedly true, our critique of this approach is that
it so general that is ends up being more rhetorical than operational: rather
than providing an avenue to study and measure how evolution might affect
specific ecosystem services, it simply gives evolution “credit” for all
ecosystem services in hopes of (legitimately, in our opinion) highlighting the
overall importance of diversity within the politics of international
conservation. As Hendry mentions, an earlier draft of our paper proposed to
redefine the term evosystem services, which we decided not to do in the end.
Instead, we developed the framework in figure 1, which situates the
contributions of different evolutionary processes to ecosystem services. This
framework accepts Faith’s very inclusive definition of evosystem services
(green), but also hones in on the nested subset of them that we believe to be
the most operational and measurable (dotted line): those that are happening
contemporarily on rapid timescales through the processes of local adaptation,
gene flow and in one instance, speciation. We named these contemporary evosystem services.
 |
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Figure 2: The nested and overlapping processes that produce
evosystem services.
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There’s no conceptual conflict between the inclusive
definition of evosystem services, as
forwarded by Faith and Hendry, and our definition of contemporary evosystem services as a nested subset within that.
But, there is perhaps a legitimate tension in the values encoded by these two
terms - which has resulted in some debate and even misunderstanding as we’ve
attempted to get this work published. The group that Hendry refers to was
concerned that conservation science and policy was heading in a direction that
put too much value on particular services that might be provided by
low-diversity or otherwise artificial types of systems (for example carbon
sequestration using fast-growing alien species) at the expense of a more
traditional conservation approach based on the preservation of biodiversity and
the intrinsic value of nature. We on the other hand wanted to lay the
foundation to study particular cases where a specific evolutionary processes
might be providing specific ecosystem service in order to better understand and
manage those systems. Therefore, it might be fair to characterize the two
approaches as supportive of macro-management vs micromanagement. The thing is,
we think both are important. We are far from presuming that it’s possible or
even desireable to micromanage all the places where rapid evolution is
occurring in order to maximize units of service. But neither do we think that
general insight about the potential value of biodiversity over the long term
can replace system specific knowledge in management scenarios. There is a
middle ground between the arrogant micromanaging of nature, and the too-general
assertion that diversity is a good thing to conserve.
Why study contemporary
evosystem services
We believe that studies exploring this rich middle ground in
an evolutionary context by looking for a positive relationship between rapid
evolution and ecosystem services are lacking, not because such cases don’t
exist, but perhaps because there hasn’t
been a conceptual or quantitative framework in which to place them. In our
paper, we therefore suggest a framework for assessing the contribution of rapid
evolution to ecosystem services and provide a number of putative examples where
rapid evolution might enhance
ecosystem services. Although there are no iron-clad examples of contemporary
evosystem services we outline some of the most promising potential
examples. We grouped these examples by
the evolutionary process, namely directional
selection and gene flow, that
might maintain or enhance the ecosystem services. It’s important to note that
these evolutionary mechanisms can function to either enhance or deplete
ecosystem services, depending on the context. Our paper highlights potential
benefits from an anthropocentric perspective because we felt that this emphasis
was lacking in the applied evolution and conservation literature so far.
One of the most compelling potential examples of how rapid
evolution might provide an ecosystem service comes from the literature on the
rapid evolution by directional selection of Daphnia. Some Daphnia
species can evolve rapidly to grow faster when feeding on toxin-containing
cyanobacteria [5–8]. This rapid evolution likely increases the
total amount of cyanobacteria consumed, potentially reducing the intensity and
duration of harmful algal blooms (HABs) associated with eutrophication. Future work assessing the contribution of
rapid evolution of Daphnia to the
reduction of phytoplankton species that cause HABs could yield an idea of the
value, in ecosystem service units (often dollars), of rapid evolution in Daphnia.
Gene flow could also provide contemporary evosystem
services. For example, several recent
models [9,10]
suggest that sufficient influx of susceptible genes from oceanic sea lice to
salmon aquaculture net-pens delays or prevents the evolution of insecticide
resistance on farms. The observation that insecticide-resistant sea lice are
absent from salmon aquaculture located in the North Pacific (where large
populations of wild salmon exist) compared to the prevalence of insecticide
resistance in the South Pacific and Atlantic (where there are small or no wild
salmon populations) seems to support this.
Other examples of putative contemporary evosystem services from gene
flow are 1) cases of genetic rescue, when migration from another population
provides an influx of genes that restores positive population growth to a
population that would otherwise perish from inbreeding depression, and 2)
mitigation of fishery size selection through gene flow from a marine protected
area.
Environmental change necessitates that evolutionary biology
and conservation be integrated and tremendous progress has been made in the
past decade. Our opinion is that
measuring and understanding contemporary evosystem services could further
contribute to this integration. Our end-goal is to spur research that
comprehensively assesses how evolution alters ecosystem services (e.g. the
services and the dis-services from rapid evolution), which we feel will yield
an improved understanding of ecosystem services today and in the future.
1 Bassar, R.D. et al. (2010) Local adaptation in
Trinidadian guppies alters ecosystem processes. Proc. Natl.
Acad. Sci. U. S. A. 107,
3616–3621
2 Rudman, S.M. et al. (2017) Evosystem Services: Rapid
Evolution and the Provision of Ecosystem Services. Trends Ecol.
Evol. 0,
3 Faith, D.P. et al. (2010) Evosystem services: an
evolutionary perspective on the links between biodiversity and human
well-being. Current Opinion in Environmental Sustainability 2, 66–74
4 Hendry, A.P. et al. (2010) Evolutionary biology in
biodiversity science, conservation, and policy: a call to action. Evolution 64, 1517–1528
5 Hairston, N.G., Jr et al. (1999) Lake ecosystems: Rapid
evolution revealed by dormant eggs. Nature 401, 446–446
6 Hairston, N.G., Jr et al. (2001) Natural selection for grazer
resistance to toxic cyanobacteria: evolution of phenotypic plasticity? Evolution 55, 2203–2214
7 Sarnelle, O. and Wilson, A.E. (2005)
Local adaptation of Daphnia pulicaria to toxic cyanobacteria. Limnol.
Oceanogr. 50,
1565–1570
8 Jiang, X. et al. (2016) Rapid evolution of tolerance
to toxic Microcystis in two cladoceran grazers. Sci. Rep. 6, 25319
9 Murray, A.G. (2011) A simple model to
assess selection for treatment-resistant sea lice. Ecol. Modell. 222, 1854–1862
10 McEwan, G.F. et al. (2015) Using Agent-Based Modelling
to Predict the Role of Wild Refugia in the Evolution of Resistance of Sea Lice
to Chemotherapeutants. PLoS One 10, e0139128
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