EntomoNews

Le quotidien anglais « The Guardian » relaie une alarmante étude centrée sur la population d’abeilles, qui se révèle de moins en moins diversifiée.

 

Publié le 23/01/2021 à 21h21

 

Source : Quarter of known bee species have not been recorded since 1990 | Environment | The Guardian, 22.01.2021 https://www.theguardian.com/environment/2021/jan/22/quarter-of-known-bee-species-have-not-been-recorded-since-1990

 

• Worldwide occurrence records suggest a global decline in bee species richness: One Earth, 22.01.2021 https://www.cell.com/one-earth/fulltext/S2590-3322(20)30651-5

 

"To make a more phylogenetically explicit analysis exploring whether bees show a differential temporal trend compared with that of their closest relatives and whether particular bee families are more endangered than others, we re-analyzed the specimen dataset and this time also retained records for two families of carnivorous apoid wasps, Crabronidae and Sphecidae, that are sister to Anthophila and for another highly diverse, non-apoid hymenopteran family, the Formicidae (ants).

The results show different patterns of species richness in records of each family with noticeable phylogenetic structure (Figure 2).

 

Long-tongued bees (Megachilidae and Apidae) show a steepening decline starting in the 2000s, whereas short-tongued bees show declines starting earlier (Andrenidae and Halictidae) or later (Colletidae). These declines in richness of recorded species relative to the average number found between 1950 and 1990 ranged from 17% for Halictidae to over 41% for Melittidae. Comparisons between Anthophila families and two families of apoid wasps sister to bees and a more distantly related family, the true ants (Formicidae), revealed contrasting trends (Figure 2).

 

While both wasp families also show declining trends, they present different patterns than bees do. Record richness of sphecid and crabronid wasps both show a smoother decrease initiating earlier than the 2000s. In contrast, ants show very little evidence of global record richness decline but rather a trend toward an increase in the number of recorded species. Although the limited number of bee families precludes a formal analysis of phylogenetic patterning, closely related families (e.g., Apidae and Megachilidae, or Colletidae and Halictidae) seem to share more similar trends in terms of timing and magnitude of species richness decline than less-related families. This hint of phylogenetic patterning becomes even more apparent when considering the two apoid wasp families, Crabronidae and Sphecidae (Figure 2).

 

Interestingly, a very similar pattern—in which bees show a strong, recent decline; wasps show a gentler decline starting earlier; and ants remain steady—was recently reported by a quite different analytical approach on a substantially different and more geographically limited dataset.

All together, family-specific trends and asymptotic richness estimates show that the apparent overall decline in global bee record richness is not driven by any particular family. Instead, a generalized decline seems to be a pervasive feature within the bee lineage."