Chromosome analyses of prickly pear cacti reveal southern glacial refugia

Feb 14, 2012
This is a polyploidy of species of Opuntia humifusa. Credit: Lucas C. Majure et al.

Analysis of chromosome number variation among species of a North American group of prickly pear cacti (nopales) showed that the most widespread species encountered are of hybrid origin. Those widespread species likely originated from hybridization among closely related parental species from western and southeastern North America. This study was published in the open access journal Comparative Cytogenetics.

The prickly pear cacti (of the genus Opuntia) are endemic to the Americas. The genus is well known for the taxonomic difficulties it poses, as a result of hybridization and morphological variation, as well as lack of intense study. Studies of chromosomal differences among species have been beneficial with regards to recognition and determination of hybrid origins of many taxa. Those studies of the differences in chromosome number have shown that a majority of species of the genus have undergone genome duplication (also known as polyploidy).

This is a hypothetical origin and subsequent dispersal of Opuntia polyploid species. Credit: Lucas C. Majure et al.

This study suggests that a group of well-known prickly pear species occurring primarily in the United States are mostly derived from and genome duplication, which occurred as a result of the genetic separation of closely related parent species through during different times of the . Those closely related species, which were restricted to the southern United States, after thousands of years of separation, came back in contact and formed the common hybrids in the group, which in turn became dominant and more successful in distribution over their progenitors. Their remained confined to the southern part of their distribution likely as a result of their non-adaptability to adverse environmental conditions, which hybrid taxa were more than able to cope with. This scenario results in the distribution pattern of species that we see today.

This study underscores that genome duplication has had an important effect on the evolution of prickly pear cacti and that understanding patterns in chromosome numbers can be used, in part, to infer the historical biogeography of certain plant groups.

Explore further: Chimpanzees prefer firm, stable beds

More information: Majure LC, Judd WS, Soltis PS, Soltis DE (2012) Cytogeography of the Humifusa clade of Opuntia s.s. Mill. 1754 (Cactaceae, Opuntioideae, Opuntieae): correlations with pleistocene refugia and morphological traits in a polyploid complex. Comparative Cytogenetics 6(1): 53-77. doi: 10.3897/CompCytogen.v6i1.2523

add to favorites email to friend print save as pdf

Related Stories

New plant species gives insights into evolution

Mar 17, 2011

A new University of Florida study shows when two flowering plants are crossed to produce a new hybrid, the new species' genes are reset, allowing for greater genetic variation.

Species reemergence after collapse: Possible but different

May 20, 2011

Species pairs that disappear through hybridization after human-induced changes to the environment can reemerge if the disturbance is removed, according to a new mathematical model that shows the conditions under which reemergence ...

A mammoth task -- sorting out mammoth evolution

May 30, 2011

Mammoths were a diverse genus that roamed across Eurasia and North America during the Pleistocene era. In continental North America, at least two highly divergent species have long been recognized – woolly ...

Recommended for you

Chimpanzees prefer firm, stable beds

7 hours ago

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

Offspring benefit from mum sending the right message

15 hours ago

(Phys.org) —Researchers have uncovered a previously unforeseen interaction between the sexes which reveals that offspring survival is affected by chemical signals emitted from the females' eggs.

Lemurs match scent of a friend to sound of her voice

Apr 15, 2014

Humans aren't alone in their ability to match a voice to a face—animals such as dogs, horses, crows and monkeys are able to recognize familiar individuals this way too, a growing body of research shows.

User comments : 0

More news stories

Revealing camouflaged bacteria

A research team at the Biozentrum of the University of Basel has discovered an protein family that plays a central role in the fight against the bacterial pathogen Salmonella within the cells. The so cal ...

Chimpanzees prefer firm, stable beds

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...