Rare plants are common where you find them

Area of Science:

• Ecology
• Evolutionary Biology
• Biogeography

Background:

• Macroecological studies often show a positive association between geographic range size and local abundance.
• This pattern is typically explained by ecological dominance of widespread species over narrowly distributed ones.
• Areas of high endemism, particularly those with neoendemics, may exhibit different patterns due to historical processes.

Purpose of the Study:

• To investigate if traditional macroecological hypotheses apply to narrowly endemic species.
• To compare local abundance and distribution patterns of narrow endemics and their widespread congeners in the northern Rocky Mountains.
• To explore potential explanations for abundance patterns in regions with high neoendemism.

Main Methods:

• Studied seven narrowly endemic species and seven ecologically similar widespread congeners in the northern Rocky Mountains.
• Estimated local abundance by counting plants in randomly located plots within randomly chosen populations for each species.
• Analyzed the association between geographic range size and local abundance for all 14 species.

Main Results:

• Contrary to expectations, a positive association between range size and local abundance was not observed.
• All seven narrowly endemic species exhibited higher local abundance than their widespread congeners.
• Ecological specialization or differences in dispersal ability were unlikely explanations for the observed patterns.

Conclusions:

• The high local abundance of narrowly endemic species may indicate recent speciation.
• These species may not have reached their full dispersal potential, reflecting ongoing evolutionary processes.
• Strictly ecological mechanisms alone cannot fully explain abundance and distribution patterns in areas characterized by neoendemism.