jmg244's picture

100_1363

Observed: 2nd January 2012 By: jmg244
S159 Neighbourhood Nature - current student
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100_1363
100_1364
Description:
Identifications
Species interactions

No interactions present.

Comments

David Jardine's picture

Why B pendula?

What characteristics have you used to exclude Betula pubescens - Downy Birch?

jmg244's picture

Thanks for help!

Thanks for help!

Pieris's picture

Birch complex

I've been interested in the differences between UK birch species for a few years, and I now suspect that divisions between pubescens and pendular are increasingly blurred. Genetically, downy birch is said to have 56 chromosomes (tetraploid) while silver has 28 (diploid). According to some studies true hybrids (42 chromosomes) are surprisingly rare, but tetraploid trees often display a wide range of native birch characteristics, from "pure" downy to "pure" silver. This is tentatively believed to be the result of the back-crossing process called introgression

According to a user on this site, AlanS, another similar species, betula celtiberica - usually said to be native to the Iberian Peninsula - is now considered native in some parts of the UK, and I've recently read an article that suggests celtiberica is native in Wales.

Trees don't read books and they don't always fit into the human boxes we like to build for them. Even among nursery silver birch, bred for their pendula characteristics, you'll sometimes find the odd hairy interloper. Though this is confusing too, because some authorities say hairiness can be a juvenile characteristic of pendula.