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Keystone Species of the Sonoran Desert.


Pachycereus schottii, Músaro, Sinita, Senita and a close up of this slow growing long lived columnar cactus occurring in the Sonoran Desert of Arizona and into northern Sonora. Sinita has limited its range to areas that do not get frost, but some cacti have shown callous from cold spells in the northern end of its range. The upper part of the stem has a dense cover of shaggy grey spines resembling an old man's beard which helps in differentiating it from another common columnar cacti within the southern end of the Sonoran, Stenocereus thurberi, Organ Pipe. Spines serve a purpose for plants, they are modified leaves offering protection from solar rays by reflecting the sun in turn reducing transpiration and shade the plant as well as offer defense from herbivores




I find it incredibly fascinating that these immobile beings are capable of protecting themselves via developing mutualistic relationships. Sinita has a mutualism with ants which offer protection for the cacti. Sinita has sugar- secreting organs known as extrafloral nectaries (EFN) located just below the aerials that attract ants. The ants reap the rewards of Sinitas sweetness by providing protection for from natural enemies (herbivorous insects) protecting the developing flower and fruit.



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Another cool relationship with insects that this cactus has is with the pyralid moth. The Female moth collects pollen from the anther on its specialized abdominal scales and deposits the pollen on the stigma, while the female moth is actively pollinating she also deposits one of her eggs in each pollinated flower where the developing larvae will feed on the ovules of Sinita. Many flowers will escape predation and produce fruits and seeds much like the obligate relationship between the Yucca moth and Yuccas including the Joshua tree.


The natural world is beyond fascinating, the way plants fight for survival much like the rest of life deserves much more than plowing them down with a backhoe, only showing interest in knowing what benefit they can offer, removing from the wild for a black-market sale or introduce into one's landscape.