Discussion

Results summary

Factor	Influence on bee presence	Influence on bee abundance
Host plant abundance	✓✓✓ Strong positive effect	✓✓✓ Strong positive effect
Connectivity	✓✓ Significant effect	✗ No significant effect
Elevation range	✓✓ Significant effect	✓✓ Significant effect

Phenology

The observed phenological patterns reflect important aspects of M. lagopoda‘s ecological strategy:

• Protandry (earlier male emergence) represents an adaptive strategy to maximize mating opportunities. By emerging before females, males can establish territories or search patterns that increase their chances of encountering females upon emergence.
• Extended female flight period reflects additional reproductive responsibilities beyond mating, including nest site selection, construction, pollen collection, and egg-laying.
• Synchronized peak activity in mid-July optimizes reproductive success by ensuring that the majority of females are receptive during maximum male availability. This timing also coincides with peak flowering of C. scabiosa, demonstrating close phenological matching between the bee and its host plant.
• The relatively narrow seasonal window compared to generalist species highlights the vulnerability of specialist bees to phenological mismatches due to climate change.

Host plants

The identified threshold of 1,034 plant stalks needed for a 50% probability of bee presence has significant implications for conservation planning. This minimum abundance likely reflects the food resources required to sustain viable bee populations. The plateau of the probability curve suggests that beyond a certain level of host plant abundance, other factors become limiting, potentially including nesting site availability.

Topography

One of the study’s most important findings is the strong positive relationship between elevation range and both bee presence and abundance. This topographic variation benefits bee populations through several mechanisms:

• Microclimatic diversity creates a wider range of temperature and moisture conditions across the habitat, potentially extending host plant flowering periods by 7-10 days
• Thermal benefits for ground-nesting bees, with south-facing slopes providing optimal temperature conditions for larval development (especially important at northern range limits)

Connectivity

The study revealed that connectivity primarily determines initial colonization rather than local abundance. This pattern suggests a classic metapopulation structure where landscape context strongly influences patch occupancy patterns through immigration and extinction processes.

The importance of population-weighted connectivity in predicting bee presence indicates that patches with larger bee populations likely produce more dispersing individuals, increasing colonization probability of surrounding habitat patches. A minimum connectivity threshold appears necessary for successful colonization, explaining why several isolated patches with abundant host plants remained unoccupied despite otherwise suitable conditions.

Conservation implications

These findings offer several practical guidelines for conservation:

• Resource thresholds: Prioritize patches with >1,000 C. scabiosa stalks to support viable bee populations
• Topography: Value topographically diverse sites even when host plant abundance is somewhat lower, as these areas provide critical microclimatic diversity and nesting opportunities
• Connectivity: Create stepping-stone habitats to connect isolated patches, maximizing habitat utilization and genetic exchange across the landscape
• Climate resilience: Maintain well-connected habitat networks that provide both microrefugia during extreme weather events and enable range shifts as conditions change
• As agricultural landscapes continue to face pressures from intensification and climate change, maintaining these landscape elements will be crucial not only for M. lagopoda but also for other specialist pollinators facing similar threats from habitat fragmentation and loss.