File:Giant Galapogean Prickly Pear (Opuntia echios var. gigantea)... next to mangroves and a beach (7429203808).jpg

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On Santa Cruz, Galapagos Islands, Ecuador

For a discussion on why Opuntia of the Galapagos are so neat, and their relationship with the endemic giant tortoises, see this image: <a href="https://www.flickr.com/photos/31867959@N04/6012346984/in/set-72157628721441167/">www.flickr.com/photos/31867959@N04/6012346984/in/set-7215...</a>

For a discussion on why I find Opuntia so neat morphologically, developmentally, and functionally: see this image: <a href="https://www.flickr.com/photos/31867959@N04/7457728654/in/set-72157628721441167/">www.flickr.com/photos/31867959@N04/7457728654/in/set-7215...</a>


      • This photo previously labeled these individuals as Opuntia echios var. echios, however, after searching the scientific literature I've discovered this designation was innaccuate. Opuntia echios is the only Opuntia species on Santa Cruz, however, there are two recognized varieties, var. echios in the north and var. gigantea in the south. These varieties were named for their morphological differentiation, however, recent genetic work with both microsatellites and ribosomal genes have determined that these varieties do don't differ genetically, with over 95% of existing genetic variability existing within localities rather than between localities of different varieties. This is interesting, because despite the lack of genetic divergence between the varieties, var. echios are small, shrub like plants with dense covering of spines, while the var. gigantea are arboreal (tree-like) plants with large robust trunks and and multiple branchings containing more sparsely spined pads. Is there a genetic basis to this differention that has evolved within very recent times, such that both populations retain overall similar genomes, or is this morphological variability simply due to regional environmental differences, which has been observed in other cacti? Who knows. There are many intermediate individuals at hybrid zone localities, but this is compatible with both models. TIme will tell...

Helsen, P., P. Verdyck, A. Tye, S. Van Dongen. 2009. Low levels of genetic differentiation between Opuntia echios varieties on Santa Cruz (Galapagos). Plant Systematics and Evolution 279:1–10.

Helsen, P., R. A. Browne, D. A. Anderson, P. Verdyck, S. Van Dongen. 2009. Galápagos' Opuntia (prickly pear) cacti: extensive morphological diversity, low genetic variability. Biological Journal of the Linnean Society 96(2): 451–461.
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Source Giant Galapogean Prickly Pear (Opuntia echios var. gigantea)... next to mangroves and a beach
Author Dallas Krentzel
Camera location0° 45′ 46.53″ S, 90° 20′ 19.79″ W Kartographer map based on OpenStreetMap.View this and other nearby images on: OpenStreetMapinfo

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This image was originally posted to Flickr by Dallas Krentzel at https://flickr.com/photos/31867959@N04/7429203808. It was reviewed on 13 May 2021 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

13 May 2021

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current18:12, 13 May 2021Thumbnail for version as of 18:12, 13 May 20212,896 × 1,936 (2.68 MB)Sentinel user (talk | contribs)Transferred from Flickr via #flickr2commons

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