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Pollen harvesting and reproductive rates in specialized solitary bees

In English

Författare

  • Markus Franzén
  • Magnus Larsson

Summary, in English

Andrena humilis is an endangered oligolectic solitary bee and has declined in recent decades throughout western Europe. The aim of this study was to explore the pollen harvesting pattern and to determine the reproductive rate in specialized andrenid bees. We measured the amount of pollen required to produce one brood-cell, the pollen harvesting rate and compared our results with data for other specialized andrenid bee species. Pollen-foraging trips were registered and the activity events (entering, leaving or digging) recorded at the nests. The mean number of pollen-foraging trips per day was 5.3 and an average bee nest was active (and open) 88 min day(-1). The bees were highly efficient in harvesting pollen and spent on average 10.7 min to complete one pollen-foraging trip. Most pollen-foraging trips (77%) were completed in less than 15 min. The duration of pollen-foraging trips increased over the day, presumably because pollen became more costly to harvest. Based on pollen counts (pollen loads on bees and pollen provisions) an average bee required 3.85 foraging trips to complete one brood cell and one bee managed to accomplish 1.37 brood cells in one day with suitable weather. In the literature we found data on an additional 19 specialized andrenid bee species. Andrena humilis seems to be extremely efficient compared with most other species, with an average trip for pollen lasting almost one hour (average for andrenid bees = 46 min). An extremely low reproductive rate seems to be a common trait among specialized bees in the family Andrenidae with an average 0.9 offspring produced per day and less than ten offspring produced during the whole lifetime. The high degree of specialisation and the low reproductive rate among andrenid bees can explain the severe decline in many species today.

Publiceringsår

2007

Språk

Engelska

Sidor

405-414

Publikation/Tidskrift/Serie

Annales Zoologici Fennici

Volym

44

Issue

6

Dokumenttyp

Artikel i tidskrift

Förlag

Finnish Zoological and Botanical Publishing Board

Ämne

  • Ecology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0003-455X