Evolutionary shifts observed in response to HIREC
Artificial selection pressures, such as those created by humans, are
capable of driving both behavioral and physiological changes in response
to selection. For example, fish with bold phenotypes can be
preferentially (and unintentionally) harvested, resulting in the
selective depletion of bold individuals (Biro & Post 2008). Differences
in personality can also result in sampling biases during scientific
sampling, with bolder individuals being caught more often (Biro &
Dingemanse 2009). Intensive fishing selects on life history traits
(growth, maturation, reproduction), but demonstrations of fishing’s
effects on behavior remained scarce until the last decade (Uusi-Heikkiläet al. 2008). Fishing methods are diverse, apparently leading to
distinct selection pressures on behavior (Diaz Pauli et al. 2015;
Arlinghaus et al. 2017). Passive fishing (e.g., using
long-lining, angling, trapping or gill nets) preferentially catch
proactive individuals (Biro & Post 2008; Arlinghaus et al.2017), while active gear (e.g., trawls or purse seines) unintentionally
targets reactive individuals (Heino & Godø 2002; Diaz Pauli et
al. 2015).
Although hunting has less pressure on wild populations in many places
compared to fisheries, it too selects for specific behavioral traits.
Madden and Whiteside (Madden & Whiteside 2014) showed for example that
shyer pheasant (Phasianus colchicus) are more likely to survive
to the hunting season than bolder ones. In wild reindeer
(Rangifer tarandus ), a long-term study also showed that hunting
pressure is correlated with an increase in flight distance over years,
suggesting that populations become shyer because of hunting pressure
(Reimers et al. 2009). Ciuti et al (Ciuti et al. 2012)
drew similar conclusions with elk (Cervus elaphus ), where
harvested individuals were bolder. In this context, hunting leads to the
same result than passive fishing, selecting for bold individuals and
therefore favoring reactive phenotypes. Inversely, the less active
animals die from active hunting techniques, such as when dogs are used
to chase animals, as seen in bear-hunting (Leclerc et al. 2019).
As a consequence, the HIRECs linked to fishing and hunting seem to favor
one coping style over the other depending on whether the harvesting
technique is active or passive.
Rapid environmental changes also may lead to evolutionary changes in the
physiology and behavior of wild populations. For instance, climate
change has been demonstrated to favor selection for highly plastic
individuals over multiple generations (Nussey et al. 2005). In
addition, multigenerational exposure to high temperatures reduces
standard metabolic rate (Pilakouta et al. 2019). Global climate
change may lead to the reduction of migratory distances in birds (Visseret al. 2009), and this phenomenon is an evolutionary response to
selection (Pulido & Berthold 2010). High plasticity, reduced metabolic
rate, and low standard metabolic rate all favor reactive phenotypes, and
we may infer that climate change is driving the evolution of reactive
phenotypes (Fig. 1.3.2). It is nevertheless worth noting that tropical
cyclones seemingly select for aggressive phenotypes (Little et
al. 2019), and in this case we would infer that proactive individuals
are better adapted to survive.
We have long known that populations evolve in response to exposure to
pollutants and with the toxification of Earth; this has become a common
driver of HIREC. Empirical studies in the lab monitoring the evolution
of behavioral and physiological traits following exposure to pollutants
are rare, despite abundant evidence of rapid evolutionary responses
(Whitehead et al. 2017; Saaristo et al. 2018). If the
exposure to only one pollutant selected one behavioral response (e.g.,
boldness or activity), it could be attenuated by a plastic behavioral
response (Saaristo et al. 2018). However, the large number and
diversity of pollutants, each with different properties, and the
possible interactions between them (Peterson et al. 2017;
Saaristo et al. 2018), as well as the method of exposure, act as
multiple environmental stressors for organisms which have to
continuously adapt to new threats and stressors. We suggest that
plasticity, a characteristic of reactive phenotypes, will be the key to
cope with the diversity of stressors created by pollution.
Urbanization, ecotourism and domestication, have all been found to
increase boldness of affected populations (Geffroy et al. 2015b).
Effects of urbanization on bird behavior have been extensively studied
and show that living in urban areas leads to reduced flight initiation
distance (Samia et al. 2015), and higher risk-taking behavior
(Miranda et al. 2013). However, adaptation to an urbanized
environment also requires substantial individual plasticity. For
instance, in response to urban noise, great tits increase their pitch
during mating calls to increase the likelihood that potential mates
receive the signal (Slabbekoorn & Peet 2003). Similar results have been
seen in killer whale (Orcinus orca ) which increased the amplitude
of their calls as a function of background noise levels related to ships
or tourism boats (Holt et al. 2009). In terms of physiology,
reduced stress reactivity was also observed for urban individuals
(Partecke et al. 2006; Atwell et al. 2012). Taken
together, these studies show that urban areas select for more proactive
individuals. In the context of domestication, individuals are often
selected for either their docility or their reproductive potential. Both
types of selection types lead to bolder individuals in response to both
human and potentially other predators (Geffroy et al. 2015b), and
reduced HPI/A reactivity (Rauw et al. 2017), which favors
proactive individuals. In the context of both, urbanization and
domestication, humans create a “human shield” (Berger 2007), where
selection pressure is relaxed and bold individuals are favored.
Disappear