Shifts in food plant abundance for flower-visiting insects between 1900 and 2017 in the canton of Zurich, Switzerland.

Adult flower-visiting insects feed on nectar and pollen and partly collect floral resources to feed their larvae. The reduction in food availability has therefore been proposed as one of the main causes for the drastic decline in flower-visiting insects in Central Europe. We compared the current (2012-2017) abundances of food plants of different groups of flower-visiting insects to that of 1900-1930 in the canton of Zurich, Switzerland. Comparisons were done separately for different vegetation types, flowering months, and groups of diurnal flower-visiting insects, such as bees, bumble bees, wasps, butterflies, hoverflies, flies, and beetles. We found a general decrease in food plant abundance for all groups of flower-visiting insects and in all vegetation types except ruderal areas. Reductions of food plant abundance were most pronounced for wetlands and agricultural fields, reflecting the massive transformation of wetlands into other habitat types and the intensified management of agricultural fields. Food plant abundance for specialized flower visitors (bees, bumble bees, butterflies) of wetlands decreased most strongly in May and for generalized flower visitors (wasps, hoverflies, flies, beetles) in July. Specialized plant species, i.e., species with few groups of flower visitors, decreased more strongly in abundance than species with many groups of flower visitors. Finally, we found a homogenization of food plant assemblages in all vegetation types except ruderal areas, where the opposite pattern emerged. Our results suggest a significant reduction in the diversity and abundance of food plants for flower-visiting insects over the past century, which has been most severe for the more specialized insect groups. The trend of insect decline, in particular those specialized on few plant species, can only be stopped by extending suitable habitats, i.e., by increasing food availability and reestablish selected plant populations.

Contemporaneous and recent radiations of the world's major succulent plant lineages.

The cacti are one of the most celebrated radiations of succulent plants. There has been much speculation about their age, but progress in dating cactus origins has been hindered by the lack of fossil data for cacti or their close relatives. Using a hybrid phylogenomic approach, we estimated that the cactus lineage diverged from its closest relatives ≈35 million years ago (Ma). However, major diversification events in cacti were more recent, with most species-rich clades originating in the late Miocene, ≈10-5 Ma. Diversification rates of several cactus lineages rival other estimates of extremely rapid speciation in plants. Major cactus radiations were contemporaneous with those of South African ice plants and North American agaves, revealing a simultaneous diversification of several of the world's major succulent plant lineages across multiple continents. This short geological time period also harbored the majority of origins of C(4) photosynthesis and the global rise of C(4) grasslands. A global expansion of arid environments during this time could have provided new ecological opportunity for both succulent and C(4) plant syndromes. Alternatively, recent work has identified a substantial decline in atmospheric CO(2) ≈15-8 Ma, which would have strongly favored C(4) evolution and expansion of C(4)-dominated grasslands. Lowered atmospheric CO(2) would also substantially exacerbate plant water stress in marginally arid environments, providing preadapted succulent plants with a sharp advantage in a broader set of ecological conditions and promoting their rapid diversification across the landscape.

The closest relatives of cacti: insights from phylogenetic analyses of chloroplast and mitochondrial sequences with special emphasis on relationships in the tribe Anacampseroteae.

Recent molecular and morphological systematic investigations revealed that the cacti are most closely related to Anacampseroteae, Portulaca and Talinum of the family Portulacaceae (ACPT clade of suborder Portulacineae). A combined analysis of ndhF, matK, and nad1 sequence data from the chloroplast and the mitochondrial genomes indicates that the tribe Anacampseroteae is the sister group of the family Cactaceae. This clade, together with Portulaca, is well characterized by the presence of axillary hairs or scales. Relationships within Anacampseroteae are characterized by a grade of five species of Grahamia s.l. from North and South America, and Grahamia australiana is found to be sister to the genera Anacampseros and Avonia. A comparison of vegetative characteristics indicates an evolutionary transition from woody subshrubs to dwarf perennial and highly succulent herbs during the diversification of Anacampseroteae. Available evidence from the present investigation as well as from previously published studies suggests that a revised classification of Portulacineae on the basis of inferred phylogenetic relationships might consist of a superfamily that includes Cactaceae and the three genera Anacampseros s.l. (including Avonia and Grahamia s.l.), Portulaca, and Talinum (including Talinella), either referred to three monogeneric families or to a paraphyletic family Portulacaceae*.

Basal cactus phylogeny: implications of Pereskia (Cactaceae) paraphyly for the transition to the cactus life form.

The cacti are well-known desert plants, widely recognized by their specialized growth form and essentially leafless condition. Pereskia, a group of 17 species with regular leaf development and function, is generally viewed as representing the "ancestral cactus," although its placement within Cactaceae has remained uncertain. Here we present a new hypothesis of phylogenetic relationships at the base of the Cactaceae, inferred from DNA sequence data from five gene regions representing all three plant genomes. Our data support a basal split in Cactaceae between a clade of eight Pereskia species, centered around the Caribbean basin, and all other cacti. Two other Pereskia clades, distributed mostly in the southern half of South America, are part of a major clade comprising Maihuenia plus Cactoideae, and Opuntioideae. This result highlights several events in the early evolution of the cacti. First, during the transition to stem-based photosynthesis, the evolution of stem stomata and delayed bark formation preceded the evolution of the stem cortex into a specialized photosynthetic tissue system. Second, the basal split in cacti separates a northern from an initially southern cactus clade, and the major cactus lineages probably originated in southern or west-central South America.

Phylogenetic relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as inferred from plastid DNA sequences.

Previous molecular phylogenetic analyses have revealed that elements of the former families Malvaceae sensu stricto and Bombacaceae together form a well-supported clade that has been named Malvatheca. Within Malvatheca, two major lineages have been observed; one, Bombacoideae, corresponds approximately to the palmate-leaved Bombacaceae, and the other, Malvoideae, includes the traditional Malvaceae (the mallows or Eumalvoideae). However, the composition of these two groups and their relationships to other elements of Malvatheca remain a source of uncertainty. Sequence data from two plastid regions, ndhF and trnK/matK, from 34 exemplars of Malvatheca and six outgroups were analyzed. Parsimony, likelihood, and Bayesian analyses of the sequence data provided a well-resolved phylogeny except that relationships among five lineages at the base of Malvatheca are poorly resolved. Nonetheless, a 6-bp insertion in matK suggests that Fremontodendreae is sister to the remainder of Malvatheca. Our results suggest that the Malvoideae originated in the Neotropics and that a mangrove taxon dispersed across the Pacific from South America to Australasia and later radiated out of Australasia to give rise to the ca. 1700 living species of Eumalvoideae. Local clock analyses imply that the plastid genome underwent accelerated molecular evolution coincident with the dispersal out of the Americas and again with the radiation into the three major clades of Eumalvoideae.

Phylogenetic relationships in the cactus family (Cactaceae) based on evidence from trnK/ matK and trnL-trnF sequences.

Cacti are a large and diverse group of stem succulents predominantly occurring in warm and arid North and South America. Chloroplast DNA sequences of the trnK intron, including the matK gene, were sequenced for 70 ingroup taxa and two outgroups from the Portulacaceae. In order to improve resolution in three major groups of Cactoideae, trnL-trnF sequences from members of these clades were added to a combined analysis. The three exemplars of Pereskia did not form a monophyletic group but a basal grade. The well-supported subfamilies Cactoideae and Opuntioideae and the genus Maihuenia formed a weakly supported clade sister to Pereskia. The parsimony analysis supported a sister group relationship of Maihuenia and Opuntioideae, although the likelihood analysis did not. Blossfeldia, a monotypic genus of morphologically modified and ecologically specialized cacti, was identified as the sister group to all other Cactoideae. The tribe Cacteae was found to be sister to a largely unresolved clade comprising the genera Calymmanthium, Copiapoa, and Frailea, as well as two large and well-supported clades. Browningia sensu stricto (excluding Castellanosia), the two tribes Cereeae and Trichocereeae, and parts of the tribes Notocacteae and Rhipsalideae formed one clade. The distribution of this group is largely restricted to South America. The other clade consists of the columnar cacti of Notocacteae, various genera of Browningieae, Echinocereeae, and Leptocereeae, the tribes Hylocereeae and Pachycereeae, and Pfeiffera. A large portion of this latter group occurs in Central and North America and the Caribbean.