Plant diversity today: Which group of plants has by far the greatest species diversity among living plants worldwide?

Introduction / Context:
Understanding global plant diversity is fundamental to ecology, evolution, and conservation. Angiosperms dominate in species numbers and ecological roles across terrestrial ecosystems, a fact that informs everything from pollination biology to crop domestication studies.

Given Data / Assumptions:

• Species counts compare major plant clades.
• Modern floras are overwhelmingly angiosperm rich.
• Gymnosperms and non-seed plant groups are far less speciose.

Concept / Approach:
Two key innovations underlie angiosperm diversity: flowers and fruits. These structures drive coevolution with pollinators and dispersers, diversify reproductive strategies, and accelerate speciation, which explains their numerical dominance relative to other groups.

Step-by-Step Solution:

Verification / Alternative check:
Biodiversity databases and botany texts agree that angiosperms number in the hundreds of thousands of species, dwarfing gymnosperms and other clades.

Why Other Options Are Wrong:

• Bryophyta, Lycophyta, and Gymnosperms have far fewer described species.
• Ferns are diverse but still much less so than angiosperms.

Common Pitfalls:
Equating ecological dominance in specific habitats with total global species richness.

Final Answer:
Angiosperms (flowering plants)