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Timema - Timema genevievae

Timema - Timema genevievae
Pinnacles National Park, North Chalone Peak, San Benito County, California, USA
May 20, 2017
On Chamise, Adenostoma fasciculatum, growing on rhyolite-derived soils.

Images of this individual: tag all
Timema - Timema genevievae Timema - Timema genevievae Timema - Timema genevievae

Geographic gaps in Timema genevievae populations
Regarding the range of T. genevievae, as presently understood, something I find interesting is the gap between the type locality "Mines Road populations" of eastern-Alameda County and those to the north in Lake County. Not only are the Lake County populations much further (~120 air miles to the north) from the type locality populations than the southernmost known Clear Creek populations (~85 air miles to the south), but they're also separated by the largest river in the state! (Well, except for maybe the Colorado? ;-). After all, Timema are flightless and relatively the Sacramento River would seem a significant barrier to northward dispersal.

But then again, it just takes one individual of a parthogenentic species to start a new population and extend the range...perhaps by somehow inadvertently hitching a ride (as a nymph?) with a bird? Or in more recent times, via a hominid?

Thanks for this interesting post, Paul
The substrate data point here is novel. To my knowledge, T. genevievae was previously recorded only from habitats with serpentinite-derived substrates (e.g. from Mines Rd & Del Puerto Canyon areas of the Diablo Range east of Fremont and San José, cited in the paper Rentz(1978) where T. genevievae was originally described; from southwest of the Walker Ridge area in Lake County, cited in Law & Crespi(2002); and from the Clear Creek area of San Benito County, documented in BG posts by Joyce Gross & Alice Abela).

Also, your location here helps fill in the gap between the recently found Clear Creek population and those of the type locality in the Mines Road area of southeast Alameda County. It would be interesting if they could be found in, say Panoche Pass area...or Pacheco Pass and Henry Coe State Park.

BTW, this can be seen to be a female from the form of the terminalia...which is consistent with T. genevievae being an asexually reproducing, parthenogenetic (all female) species. In fact, T. genevievae was the first Timema species recognized as parthenogenetic...and research indicates it is one of the most ancient of the five currently known parthenogenetic Timema species (having maintained asexual reproduction for ~1,000,000 Schwander et. al.(2011)).

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