Habitat fragmentation can affect species for multiple generations beyond the initial disturbance. Even once the landscape is stable, the new configuration can influence traits such as individual dispersal, species interactions, and resource availability, all of which have impacts for offspring.
When it comes to plants, this means that habitat fragmentation can potentially impact a huge number of progeny. Not only do changes in the landscape impact the quantity of progeny produced, but also the genetic and biological quality of those progeny. Understanding how plants respond to fragmentation, and how their progeny are altered as a result, is important for predicting which plant species will persist under future land use changes and how these altered plants will affect the communities around them.
A recent review gathered over 100 years of research for a meta-analysis that summarizes global response patterns on plant progeny performance in response to habitat fragmentation. Using almost 200 publications, it included over 150 plant species from several biomes of the world. These species represented different plant types (trees, shrubs, perennial herbs, epiphytes and vines), mating systems (outcrossing, mixed mating, and selfing), and pollination vectors (wind, insect, and vertebrate).
The analysis showed that, overall, progeny sired in fragmented habitats have decreased genetic diversity and outcrossing rates, and increased inbreeding and correlated paternity. This held true for plants regardless of mating systems and pollination vector, with the exception of vertebrate-pollinated plants, where fragmentation had no significant effect on any of these genetic variables.
The analysis also showed that progeny generated in fragmented conditions have, on average, lower vigor than progeny sired in continuous habitat. However, this effect differed by mating system, with stronger negative effects on outcrossing- than mixed-mating plant species, and by pollination vector, with no effects on vertebrate-pollinated plants.
The results of meta-analysis reveal that empirical evidence supports theories that habitat loss and fragmentation have negative ecological and genetic consequences for plants. Habitat fragmentation not only reduces reproductive output and genetic diversity in adult plant populations, but it also carries on these effects into the performance of subsequent generations. The exception to this general pattern is in vertebrate-pollinated plants, where the ability of the pollinators (i.e. birds and bats) to travel long distances likely negates the deleterious effects of fragmentation.
Recent debate over the consequences of landscape vs. patch-scale effects has complicated matters on how we view fragmentation and biodiversity. However, studies such as this support the idea that, regardless of the effect of scale, in angiosperms the effects of habitat fragmentation seem real. Without intervention to restore connectivity and maintain gene flow, genetic erosion is likely to continue as humans modify the landscape even further. Intensive restoration of the landscape and long-term protection of plant populations will be necessary to ensure that biodiversity persists.
Aguilar, R., Cristóbal‐Pérez, E.J., Balvino‐Olvera, F.J., de Jesús Aguilar‐Aguilar, M., Aguirre‐Acosta, N., Ashworth, L., Lobo, J.A., Martén‐Rodríguez, S., Fuchs, E.J., Sanchez‐Montoya, G. and Bernardello, G., et al. 2019. Habitat fragmentation reduces plant progeny quality: a global synthesis. Ecology Letters. DOI: 10.1111/ele.13272.