cities. Furthermore, railway verges are habitats and thus potential sources for these
species for other habitats. The positive urbanisation effect that we found on these
species, suggests that their presence is more linked to the urban context (sources,
abiotic conditions) than railways connectivity. More studies are needed to assess
railways connectivity in other landscapes and for a greater number of species.
Railways as Barriers in an Agricultural Landscape
(Transversal Connectivity)
Linear infrastructures such as railways can be barriers to the movements of individuals and, hence, may have strong impacts on populations (see Chap. 4). We
tested if this effect existed or if there was transversal connectivity between the two
sides of a high-speed railway for the common butterfly Pyronia tithonus
(Vandevelde et al. 2012). We hypothesised that P. tithonus individuals, if captured
on the railway verge on one side of the railway and translocated to the other side in
a similar habitat, will not be able to return to their original site because of the
alleged barrier effect of the railroad. This hypothesis is based on empirical evidence
that P. tithonus shows homing behaviour when displaced: when given a choice
between a familiar and an unfamiliar habitat, these butterflies prefer to return to
their familiar habitat (Conradt et al. 2001).
Pyronia tithonus is a European Satyrinae (Nymphalidae) occurring in several
grassland habitats, usually in association with scrub or hedges. Mean life-span of adults
ranges from 3.5 to 8 days (Brakefield 1987). P. tithonus produces only one generation
per year and uses several grasses as host plants (Merckx and Van Dyck 2002).
We captured, marked and displaced 152 individuals in two different locations.
One-third of the butterflies were released at a capture plot, one-third on the other
side of the railway (in a similar habitat) and one-third on the same side but 100 m
away from the capture plot. Many (31%) butterflies crossed the railway, showing
homing behaviour. There were even a slightly greater number of exchanges
between the two release plots across the railway (12) than between the two release
plots along the railway (8); the opposite of what we would expect if railways acted
as a barrier to butterfly movements.
Even if based on a small sample, our results tend to show that contrary to wide
busy roads (Munguira and Thomas 1992), high-speed railways, which are narrower
and have infrequent traffic, are not barriers to Gatekeeper movements. These results
also suggest that in a predominantly agricultural-intensive context, railways with
large grassy verges could be substitution habitats for grassland butterflies, with no
effect of the 20-m-wide-ballast-tracks. Furthermore, it suggests that passing trains
do not have an impact on P. tithonus movements. However, the mortality risk from
train traffic still has to be properly assessed, as well as the possible effects of the
railway structure (tracks on cuttings vs. those on embankments; wide vs. narrow
verges) on movements of individuals.
16 Ecological Roles of Railway Verges in Anthropogenic Landscapes …
271
species for other habitats. The positive urbanisation effect that we found on these
species, suggests that their presence is more linked to the urban context (sources,
abiotic conditions) than railways connectivity. More studies are needed to assess
railways connectivity in other landscapes and for a greater number of species.
Railways as Barriers in an Agricultural Landscape
(Transversal Connectivity)
Linear infrastructures such as railways can be barriers to the movements of individuals and, hence, may have strong impacts on populations (see Chap. 4). We
tested if this effect existed or if there was transversal connectivity between the two
sides of a high-speed railway for the common butterfly Pyronia tithonus
(Vandevelde et al. 2012). We hypothesised that P. tithonus individuals, if captured
on the railway verge on one side of the railway and translocated to the other side in
a similar habitat, will not be able to return to their original site because of the
alleged barrier effect of the railroad. This hypothesis is based on empirical evidence
that P. tithonus shows homing behaviour when displaced: when given a choice
between a familiar and an unfamiliar habitat, these butterflies prefer to return to
their familiar habitat (Conradt et al. 2001).
Pyronia tithonus is a European Satyrinae (Nymphalidae) occurring in several
grassland habitats, usually in association with scrub or hedges. Mean life-span of adults
ranges from 3.5 to 8 days (Brakefield 1987). P. tithonus produces only one generation
per year and uses several grasses as host plants (Merckx and Van Dyck 2002).
We captured, marked and displaced 152 individuals in two different locations.
One-third of the butterflies were released at a capture plot, one-third on the other
side of the railway (in a similar habitat) and one-third on the same side but 100 m
away from the capture plot. Many (31%) butterflies crossed the railway, showing
homing behaviour. There were even a slightly greater number of exchanges
between the two release plots across the railway (12) than between the two release
plots along the railway (8); the opposite of what we would expect if railways acted
as a barrier to butterfly movements.
Even if based on a small sample, our results tend to show that contrary to wide
busy roads (Munguira and Thomas 1992), high-speed railways, which are narrower
and have infrequent traffic, are not barriers to Gatekeeper movements. These results
also suggest that in a predominantly agricultural-intensive context, railways with
large grassy verges could be substitution habitats for grassland butterflies, with no
effect of the 20-m-wide-ballast-tracks. Furthermore, it suggests that passing trains
do not have an impact on P. tithonus movements. However, the mortality risk from
train traffic still has to be properly assessed, as well as the possible effects of the
railway structure (tracks on cuttings vs. those on embankments; wide vs. narrow
verges) on movements of individuals.
16 Ecological Roles of Railway Verges in Anthropogenic Landscapes …
271