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The four-subfamily subdivision of Rosaceae has been recently replaced by a three-subfamily scheme. The re-circumscribed Rosoideae lacks a solid and well-resolved phylogeny on which a classification can be based. In this study, we sampled 56 genera presumably belonging to Rosoideae and 10 genera belonging to other subfamilies or families and used 12 chloroplast regions ( mat K, rbc L, trn L, trn L–F, ndh F, ycf 1, trn C– ycf 6, trn S–G, trn S, psb A– trn H, rpo C1 and trn S– ycf 9) to reconstruct their phylogeny. Our results confirmed (1) the exclusion of Rhodotypos and Kerria from Rosoideae and their inclusion in the subfamily Amygdaloideae and (2) the exclusion of Chamaebatia , Cercocarpus , Dryas and Purshia (including Cowania ) from Rosoideae and their inclusion in Dryadoideae, the sister subfamily of Rosoideae. Within Rosoideae, there are six strongly supported lineages that correspond to six tribes: Ulmarieae, Colurieae, Rubeae, Roseae, Agrimonieae and Potentilleae. We dated the divergence of Rosoideae back to approximately 69.77 million years ago (Mya; 95% HPD = 61.28–78.33 Mya) and that of the tribes within Rosoideae to from 10.42 to 40.02 million years ago (Mya; 95% HPD = 4.73–59.08 Mya). The subfamily is probably of North American and Asian origin and thrives in the northern hemisphere, especially in Asia. After re-circumscriptions of several genera, there are 36 genera recognized in Rosoideae.

Oncerometopus atriscutis Knight and Prepops rubroscutellatus (Knight) are plant bugs of the tribe Restheniini and subfamily Mirinae, largest of the eight mirid subfamilies. Both species were described in the late 1920s from a few locales in Arizona and New Mexico (also Colorado in the case of P. rubroscutellatus); their host-plant relationships have remained undocumented. We give additional distribution records of O. atriscutis from Arizona (3 counties, 6 sites), New Mexico (11 counties, 35 sites), and Texas (3 counties, 3 sites; new state record) and P. rubroscutellatus from Arizona (3 counties, 3 sites) and New Mexico (9 counties, 29 sites). Their seasonal histories are based mainly on regular sampling of Apache plume, Fallugia paradoxa (D. Don) Endl. ex Torr.; Rosaceae), from mid-July 2009 to mid-May 2012 at a Chihuahuan Desert site east of Las Cruces (Doña Ana Co.), New Mexico, where the bugs were syntopic. Supplemental data on seasonality were obtained from periodic collections from Apache plume in southwestern states. Regular sampling near Las Cruces, as well as supplemental collecting, indicated that both restheniines are bivoltine. Overwintered eggs hatched during the last two weeks of March at the main study site, and first-generation adults of both species appeared by mid-April and were present until early May. Nymphs of a second generation were present from early June to October (fifth instars occasionally were found in November), with adults present as late as the end of November. In the Southwest, both plant bugs were found only on Apache plume; the 1926 record of O. atriscutis from “Cowania sp.” (Rosaceae) in the Chiricahua Mountains of Arizona is considered an incidental occurrence of adults or a misidentification of Fallugia paradoxa.

Nitrogen fixing trees and shrubs may be useful in revegetation efforts. The possibility that soil and environmental factors may influence a soil's capability to produce nodulated seedlings was explored. Purshia tridentata and Cowania mexicana var. Stansburiana seedlings were grown in greenhouse trials using ten soils from native sites for each of the two genera. Treatments included a control and a six mmole nitrogen amendment as NH₄NO₃ for both surface and subsurface samples. Nodulation was often sparse for seedlings grown in surface collected samples. Although nodulation was usually better in subsoil samples, even some subsoils produced few or no nodules. Nitrogen additions inhibit nodulation and although soil nitrogen may be inhibitory in some unamended surface soils it is probably not a general cause of sparse nodulation. Nodule masses showed the same trends as nodule number but varied less with treatment and depth of soil source. Seedlings compensated for sparse nodulation with an increase in mass per nodule. Incidence of nodulation was related to some soil and environmental factors. Multiple regression analysis explained a substantial portion of nodulation variability. Soils from lower elevations with less precipitation did not produce well nodulated seedlings even in well watered greenhouse trials. Micronutrient cations, potassium, and phosphorus are positively correlated with nodulation incidence. The two genera were generally similar in nodulation responses to soil and environmental factors.

Examination of the type collections of Purshia subintegra (Kearney) Henrickson, a critical and necessary step, during the study of apparent hybridization between central Arizona Purshia, revealed that a holotype had not been designated by Kearney for the basionym, Cowania subintegra. Additionally, it was found that, though a holotype had not been designated, isotypes had been recognized. Label data of all specimens bearing the isotype designation was found to be discordant with Kearney's protologue in site location and, excepting POM 282632, collection number. The specimen accessioned as ARIZ 93633, one of two Cowania subintegra specimens (Darrow and Benson 10891) at ARIZ, is designated lectotype.

Wildland shrubs have gained considerable attention in recent years due to increasing recognition of their values as animal feed, as wildlife habitat, and for land reclamation. Better management of the shrub resource will be possible through clearer taxonomic identification and better understanding of phylogenetic relationships. This study applied polyacrylamide gel electrophoresis and further developed this technique to address genetic relationships among 16 paired shrub species (genera: Artemisia, Chrysothamnus, Atriplex, Ceratoides, Sarcobatus, Purshia, Cowania, and Cercocarpus [Compositae, Chenopodiaceae, Rosaceae]). Cluster analysis of similarity values for total protein and 14 isoenzyme systems gave patterns of species relationships expected from classical morphological grounds with two minor exceptions. Isoenzyme analyses showed promise for solving taxonomic, phylogenetic, and population genetics problems.

The structure of actinorhizal nodules of Cowania subintegra (common name: Arizona cliffrose) was studied by transmission electron microscopy. Morphological forms of the actinomycete in host cortical cells included septate hyphae and nonseptate elliptically shaped vesicles. Vesicles were distributed randomly throughout the host cytoplasm and were surrounded by host plasma membrane. No sporangia were observed in these nodules. Both endophytic hyphae and endophytic vesicles contained nucleoid regions, vesicular mesosomes, and rosette-shaped granules. The fine structure of the microsymbiont was similar to that found in other Frankia-induced root nodules, especially those in other members of the Rosaceae.

All possible graft combinations of Cowania mexicana, Fallugia paradoxa, Purshia glandulosa, and P. tridentata. were produced in tissue culture and transferred to the greenhouse. When grown in nodulating soils, only combinations of Purshia and Cowania have produced effective actinorhizal nodules. Combinations involving Fallugia exhibited substantial growth, but few survived for more than 20 wk. No heterografts with Fallugia scions have survived for more than 60 wk, although a small number of Purshia scions on Fallugia rootstock have survived and continue to exhibit normal growth.

Successful grafts between Fallugia paradoxa and Cowania mexicana were prepared using shoots proliferated in vitro and rootstocks of aseptically germinated seedlings. Microscopic examination through the graft union revealed vascular connections between the scion and rootstock. The Actinomycete, Frankia sp., can fix nitrogen in symbiosis with roots of C. mexicana but not with F. paradoxa. Successful grafts between the rootstock of an N-fixing genus and the scion of a non-N-fixing genus may be useful in studying the process of N fixation in nonlegume actinorhizal plants and may also have potential commercial applications for certain rosaceous crops.