1.4.2 Persistence Versus Migration
The high mountain biota includes cases of log-term persistence within a given range
of some species. They went through contrasting climatic conditions such as those
corresponding to the Quaternary succession of cold and temperate periods. In this
sense, some ancient plant and animal endemics have apparently remained from
Pliocene onwards roughly within their present range (Schmitt 2017). Interestingly,
most of these species, called paleoendemic, correspond to more or less isolated tips
in phylogenetic trees and nowadays are found in conservative habitats (Garcia et al.
2012) and are focus of conservation biology research (Segarra-Moragues and
Catalan 2010). Aside from these survivors, however, most probably there were
close relatives that vanished through changing ecological conditions. In parallel,
more dynamic ecosystems (e.g., grasslands) must have enhanced radiating speciation, which is well exemplified in rich taxonomic complexes exhibiting narrow
endemicity at the levels of species or lower (García and Gómez 2007). Therefore, a
high mountain with fragmented landscapes in which different habitats are densely
arranged has been a noticeable arena for various biological groups where fine-scale
isolation has favored speciation. All in all, the altitudinal gradient imposes contrasting environmental conditions and any overall shift in climate results in pressure
upon the current altitudinal species distribution (Fig. 1.6).
In simple terms, the response to an environmental change beyond the ideal
conditions for a species consists of two options (Berg et al. 2010). Either persisting
by acclimation (and eventually adaptation) to the new situation (Lapenis et al. 2005;
Reich et al. 2016) or migrating following the direction of suitable conditions for the
species (Hickling et al. 2006). The actual response depends on both the characteristics of the species and the pace at which environmental changes occur
(Theurillat and Guisan 2001). In extreme cases, a third option may occur, the
sudden collapse and local extinction of the population (Penuelas et al. 2013b).
With warming in the mountains, we can expect an upwards shift of the populations. This may apply from flying invertebrates (Konvicka et al. 2003) to trees
(Seppa et al. 2002). However, the time response may be markedly different
(Dullinger et al. 2004), with a variety of factors playing a role. Not only matters the
capacity for displacement and generation time, but also the interaction with other
species (Laiolo and Obeso 2017). Dynamics at ecotones between mountain forest
belts is particularly difficult to predict (Dullinger et al. 2005) and simulate (Wiegand
et al. 2006); the two, or more, tree species implied may not be responding in the
same way at the climate change (Rabasa et al. 2013). Therefore, we can expect not
only the displacement of the vegetation in the mountains, but also variations in the
relative thickness of the belts, or even the number of belts. At present, except for the
top mountain (Rixen and Wipf 2017), vegetation response to climate change may
be still obscured for concurrent land use shifts. The response of invertebrates may
be less ambiguous at the current stages of mountain warming (Wilson et al. 2005).
The different velocity of reaction may be causing a rearrangement of species
interactions, which increases the difficulty in predicting the ecological outcomes of
1 The High Mountain Conservation in a Changing World
19
The high mountain biota includes cases of log-term persistence within a given range
of some species. They went through contrasting climatic conditions such as those
corresponding to the Quaternary succession of cold and temperate periods. In this
sense, some ancient plant and animal endemics have apparently remained from
Pliocene onwards roughly within their present range (Schmitt 2017). Interestingly,
most of these species, called paleoendemic, correspond to more or less isolated tips
in phylogenetic trees and nowadays are found in conservative habitats (Garcia et al.
2012) and are focus of conservation biology research (Segarra-Moragues and
Catalan 2010). Aside from these survivors, however, most probably there were
close relatives that vanished through changing ecological conditions. In parallel,
more dynamic ecosystems (e.g., grasslands) must have enhanced radiating speciation, which is well exemplified in rich taxonomic complexes exhibiting narrow
endemicity at the levels of species or lower (García and Gómez 2007). Therefore, a
high mountain with fragmented landscapes in which different habitats are densely
arranged has been a noticeable arena for various biological groups where fine-scale
isolation has favored speciation. All in all, the altitudinal gradient imposes contrasting environmental conditions and any overall shift in climate results in pressure
upon the current altitudinal species distribution (Fig. 1.6).
In simple terms, the response to an environmental change beyond the ideal
conditions for a species consists of two options (Berg et al. 2010). Either persisting
by acclimation (and eventually adaptation) to the new situation (Lapenis et al. 2005;
Reich et al. 2016) or migrating following the direction of suitable conditions for the
species (Hickling et al. 2006). The actual response depends on both the characteristics of the species and the pace at which environmental changes occur
(Theurillat and Guisan 2001). In extreme cases, a third option may occur, the
sudden collapse and local extinction of the population (Penuelas et al. 2013b).
With warming in the mountains, we can expect an upwards shift of the populations. This may apply from flying invertebrates (Konvicka et al. 2003) to trees
(Seppa et al. 2002). However, the time response may be markedly different
(Dullinger et al. 2004), with a variety of factors playing a role. Not only matters the
capacity for displacement and generation time, but also the interaction with other
species (Laiolo and Obeso 2017). Dynamics at ecotones between mountain forest
belts is particularly difficult to predict (Dullinger et al. 2005) and simulate (Wiegand
et al. 2006); the two, or more, tree species implied may not be responding in the
same way at the climate change (Rabasa et al. 2013). Therefore, we can expect not
only the displacement of the vegetation in the mountains, but also variations in the
relative thickness of the belts, or even the number of belts. At present, except for the
top mountain (Rixen and Wipf 2017), vegetation response to climate change may
be still obscured for concurrent land use shifts. The response of invertebrates may
be less ambiguous at the current stages of mountain warming (Wilson et al. 2005).
The different velocity of reaction may be causing a rearrangement of species
interactions, which increases the difficulty in predicting the ecological outcomes of
1 The High Mountain Conservation in a Changing World
19