Endemism Flashcards
What is endemism?
Restricted spatial distribution of a species.
Often leads to / associated with low levels of genetic variation –> vulnerable to extinction
How are endemic species distributed?
Not evenly distributed!
Islands often have a higher than normal level of endemism due to their isolation.
Areas with high levels of endemism are often reffered to as hotspots
What are the causes of endemism
Extinctions and/ or radiations - one species radiates and then the intial species becomes extinct
Disperal with extinction and / or differentiation- one species disperes then initial species becomes extinct and the new one may adapt to an area
Vicariance- One large gene pool separates into 2 which are evolutionary independent - genepool fragmentation.
What are some possible methods of dispersal?
Wings, swimming, seed carrying, wind, water
What causes gene-pool fragmentation?
Climatic or geological events e.g. climate change.
Populations are discontinous
Geneflow reduced often zero.
What affects the number of endemics?
Distance of geographical separation
Time since separation –> when did speciation occur- paleo or neo endemics
Size of geographical area
Ecological diversity –> how many avaliable niches?
What are the main trends in endemism in Europe?
Concentrated in areas of mediterrean climate
Correlated for mammals birds and reptiles
Plants are able to speciate in a smaller area than vertebrates.
How would you compare British Endemics to those found in the Balearic Islands?
All british endemic plants are neoendemics which are mostly allopolyploids, infra-specific taxa or apomictic variants
7% of species are endemic many of which are paleoendemics, some diploids and polyploids. Most endemic animals are innvertebrates exp. midwife toad.
Read Lavergne et al. 2004
Describe the habitat of midwife toad
Isolated damp cervices, and waterfall pools
Places where viperine snakes like
Describe the life cycle of the mallorcan midwife toad
Female produces a string of eggs
Male carries them around on his hind legs keeping them moist until they hatch when he releases them into the water. They live as tadpoles for up to 1 year.
Had to be reintroduced to Mallorca due to decrease in numbers, now numbers slowly increasing
How does speciation occur in the meditterean
Ecological speciation –> reproductive isolation
Speciation may occur due to complete geographical isolation following tectonic split
Persistance due to lack of competition in rocky habitats –> lots of small endemics which can take advantage of the niches avaliable
What are the affects of the founder effect
Narrow genetic basis due to few individuals and lack of variation –> few alleles
Similar to bottlenecking
Genetic Diversity and Distribution
Describe the general trend in endemics on islands
Generally have lower levels of genetic variation in endemics in island populations compared to mainland.
Genetic variation in endemics is lower than in non-endemics.
