Asterids

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Asterids are a large group of dicotyledonous flowering plants, encompassing about 80,000 species spread across 13 orders, many families, and numerous genera. They are part of the clade Eudicots, one of the two major groups into which all dicots have been divided. The name "Asterids" is derived from the type family Asteraceae, which is the largest family within this group, containing species such as daisies, asters, and sunflowers. This group is characterized by one or more of the following features: sympetalous flowers (having united petals), inflorescences in the form of capitula, presence of iridoids, and epipetalous stamens (stamens attached to petals).

Classification

The classification of Asterids has undergone significant changes with the advent of molecular phylogenetic studies. Traditionally, the group was divided into two main subgroups: the Lamiids and the Campanulids, based on morphological characteristics. However, modern phylogenetic analyses have refined these classifications to better reflect the evolutionary relationships among these plants.

Lamiids

The Lamiids, also known as the "Euasterids I", include several well-known orders such as Lamiales, Solanales, and Boraginales. This group is notable for containing many aromatic herbs and shrubs, including families like Lamiaceae (mint family), Boraginaceae (borage family), and Solanaceae (nightshade family), which includes important species such as tomatoes, potatoes, and tobacco.

Campanulids

The Campanulids, or "Euasterids II", encompass a diverse range of plants including the orders Asterales, Apiales, and Dipsacales. The Asteraceae family, belonging to the Asterales order, is the largest within the Campanulids and includes a wide variety of flowers such as daisies, chrysanthemums, and lettuces. Other notable families within the Campanulids include Apiaceae (carrot family) and Campanulaceae (bellflower family).

Evolution and Distribution

Asterids are believed to have originated during the Cretaceous period, with their rapid diversification occurring due to a combination of evolutionary innovations and ecological opportunities. They are now distributed globally, from tropical to temperate regions, and inhabit a wide range of habitats. Their success is partly attributed to the evolution of sympetalous flowers, which are more efficient in attracting pollinators.

Economic and Ecological Importance

Many Asterids are of significant economic importance, providing food, spices, medicines, and ornamentals. The Solanaceae family, for example, includes key agricultural crops such as tomatoes, potatoes, and eggplants. The Lamiaceae family is renowned for its aromatic herbs like mint, basil, and rosemary, which are essential in culinary and medicinal applications. Additionally, many species within the Asterids play crucial roles in their ecosystems, serving as primary producers, pollinators, and food sources for a variety of organisms.

Conservation

While many Asterid species are abundant and widely cultivated, others are threatened by habitat loss, climate change, and overexploitation. Conservation efforts are essential to protect these species and maintain the biodiversity and ecological balance of their habitats.