Rosa Rubicondior: Malevolent Design - How The Success Of A Honey Bee Parasite Is Assured

Varroa mites on honey bee pupa.

By Unknown author - Kika De La Garza Subtropical Agricultural Research Center
Weslaco, Texas, USA, Public Domain, Link

Varroa mites escape the evolutionary trap of haplodiploidy | Nature Communications

Creationists like to portray living things as products of a single act of creation in which every species was equipped with its characteristic form and method of reproduction from the outset. In that view, reproductive systems should be fixed features of separately created “kinds”, not historically contingent arrangements that can be remodelled by natural selection.

Biology reveals something very different. Even such fundamental characteristics as sex determination, chromosome number and the balance between sexual and asexual reproduction can evolve. Existing developmental mechanisms are modified, discarded or repurposed according to whether the resulting variations leave more descendants. Evolution has no predetermined direction, no obligation to proceed from “simple” to “complex” and no rule forbidding a lineage from reacquiring a feature resembling one possessed by its ancestors.

An international team of researchers has now discovered an especially striking example in Varroa destructor, the globally invasive parasitic mite that feeds on honeybees and transmits damaging viruses between them. Its reproductive system appears to have reversed what was once regarded as an evolutionary one-way street.

Like many mites, bees, wasps and ants, Varroa was believed to be haplodiploid. In conventional haplodiploidy, females develop from fertilised eggs and possess two sets of chromosomes, while males develop from unfertilised eggs and possess only one. Consequently, a haploid male can transmit only the single copy of each gene inherited from his mother.

That should present Varroa with a serious evolutionary handicap. A female mite enters a honeybee brood cell shortly before it is sealed and produces one son followed by several daughters. The siblings mate with one another inside the cell, producing generation after generation of extreme inbreeding. Combined with the population bottlenecks associated with invading new hosts and new geographical regions, this should rapidly erode genetic diversity and limit the parasite’s ability to adapt.

However, by tracing genetic variants through three-generation pedigrees, Nurit Eliash and colleagues discovered that Varroa is not conventionally haplodiploid after all. Its females produce sons parthenogenetically, but those sons initially inherit both copies of their mother’s genome and are effectively genetic clones of her. Although DNA is subsequently eliminated from some of the males’ body cells, their reproductive lineage retains access to both maternal copies, either of which can be transmitted to a daughter.

This unusual arrangement slows the loss of heterozygosity caused by repeated sibling mating, preserves a larger effective population size and gives the mites more evolutionary potential than conventional haplodiploidy would allow. It helps explain how a parasite founded by relatively few individuals can retain enough variation to colonise new regions and evolve responses to the measures humans use against it.

The researchers interpret this system as a rare evolutionary reversion from haplodiploidy, long considered an almost irreversible evolutionary endpoint. It is not a simple restoration of the ancestral condition. Evolution has instead produced a novel reproductive system that retains the parthenogenetic production of males while recovering an important advantage of diploidy. As so often happens, natural selection has worked with inherited developmental machinery and arrived at a functional compromise—not by foresight or design, but because mites possessing it left more descendants.

This is precisely the sort of messy, historically constrained result that evolutionary theory predicts and creationism cannot explain. There are no immutable reproductive “kinds” and no ladder of progress along which evolution must travel in one direction. There are populations, inherited variations and selection operating generation after generation—sometimes carrying evolution along a new route and sometimes producing something that resembles a return towards an ancestral state.

There is an additional problem here for anyone wishing to attribute biological adaptations to a benevolent intelligent designer. This remarkable reproductive innovation benefits a parasite that wounds honeybees, spreads debilitating viruses and can contribute to the destruction of entire colonies. Evolution explains such an outcome without difficulty: selection favours whatever enables the mites to survive and reproduce, regardless of the suffering inflicted upon their hosts. Invoking design merely replaces that natural explanation with a designer apparently devoted to making a destructive parasite more adaptable.

The team’s findings are reported in the open-access journal Nature Communications.

Varroa destructor^ from obscure Asian parasite to global honeybee scourge.

An ancient association with Asian honeybees

Varroa destructor evolved as a brood parasite of the eastern or Asian honeybee, Apis cerana, across mainland and eastern Asia. During their long association, host and parasite influenced one another’s evolution. A. cerana developed defences including grooming, detecting and removing infested brood, and restricting successful mite reproduction largely to drone brood. Consequently, infestations are generally less destructive than they are in western honeybees.

A human-assisted host switch

The western honeybee, Apis mellifera, evolved in Europe, Africa and western Asia and had no evolutionary history with Varroa. When beekeepers introduced it into eastern Asia, it encountered mites living on A. cerana. At least two V. destructor lineages independently acquired the ability to reproduce on the new host, probably around the middle of the twentieth century. The resulting relationship was badly unbalanced: A. mellifera lacked the Asian bee’s evolved defences, while the mites could reproduce in both worker and drone brood. Research on parallel evolution of resistance places the species-barrier crossing at approximately the 1950s.

Only two lineages founded the global invasion

Although numerous mitochondrial lineages of V. destructor occur on Asian honeybees, almost the entire infestation of A. mellifera originated from two: the Korean K1 lineage and the Japan/Thailand J1 lineage. K1 became overwhelmingly dominant across most of the world, while J1 remained more geographically restricted. Genetic analyses describe these invasive populations as two partly isolated, nearly clonal lineages. Solignac and colleagues’ population study documents this remarkably narrow origin.

Globalisation completed the invasion

Movement of managed colonies, queens and package bees carried the mites far beyond Asia. From the 1960s onwards they spread through Europe and subsequently reached most beekeeping regions:

Date Event

c. 1950s Independent Korean and Japanese host switches to A. mellifera

1960s–1970s Rapid spread through the Soviet Union, eastern Europe and elsewhere

1987 Detected in the continental United States

1992 Detected in Britain

2022 Established in Australia after decades of exclusion

Within countries, drifting bees, colony robbing, swarming and movement of managed hives continued the spread. The history is therefore partly an evolutionary event and partly an unintended consequence of human trade.

For nearly a century it had the wrong name

A mite collected from A. cerana in Java was described in 1904 as Varroa jacobsoni. Mites spreading through western honeybees were subsequently given the same name because the different forms looked so similar. In 2000, Denis Anderson and John Trueman combined mitochondrial DNA evidence, reproductive isolation and morphology to show that “V. jacobsoni” was actually a complex of cryptic species. They gave the mainland Asian species responsible for the global pandemic the appropriately ominous name Varroa destructor. The true V. jacobsoni remained a separate Southeast Asian species. The USDA’s historical account explains this taxonomic correction.

The evolutionary process is happening again

The story did not end with V. destructor. In 2008, populations of the true V. jacobsoni were found reproducing on A. mellifera in Papua New Guinea. Genetic evidence indicates several independent host shifts from local A. cerana, some apparently representing intermediate stages in the colonisation process. This provides an unusually direct example of parasite evolution in progress. Roberts and colleagues documented these repeated host shifts.

A parasite–virus alliance

Female mites feed principally on the honeybee’s fat-body tissue and transmit viruses—most notably deformed-wing virus—directly between bees. The mite did not create these viruses, but its spread changed their ecology and favoured virus variants suited to mite-mediated transmission. Thus, the modern crisis is the evolving interaction of three participants: bee, mite and virus.

The genetic paradox behind the new study

The global invasion began with extremely few mite lineages and reproduction involves repeated brother–sister mating. Both should have caused a crippling loss of genetic diversity. Nevertheless, V. destructor has continued to adapt to new environments, different bee populations and acaricides. The newly discovered production of functionally diploid sons helps explain how it retained more genetic variation than conventional haplodiploidy should permit.

Date	Event
c. 1950s	Independent Korean and Japanese host switches to A. mellifera
1960s–1970s	Rapid spread through the Soviet Union, eastern Europe and elsewhere
1987	Detected in the continental United States
1992	Detected in Britain
2022	Established in Australia after decades of exclusion

Abstract
Genetic diversity is essential for populations adapting to environmental-changes. Following genetic bottlenecks, invasive species often have reduced diversity, yet must rapidly adapt to novel environments. This paradox is especially pronounced in parasites, which face repeated transmission bottlenecks and anthropogenic countermeasures. The challenge of maintaining diversity in the short-term intensifies in haplodiploid species, where males inherit and transmit only half of their mother’s genome, limiting effective population size. To examine how such species may maintain adaptability, we study inheritance in Varroa mites (Varroa destructor), the globally invasive honey bee parasite. Using three-generation pedigrees, we find that Varroa is not haplodiploid, as previously thought. Rather, females produce diploid clone sons who transmit either copy of their mother’s genome to daughters. This system slows reduced heterozygosity loss under sib-mating, compared to ancestral haplodiploidy, increasing effective population size and adaptability. Our findings reveal a rare reversion from haplodiploidy, long considered an evolutionary end state, and suggest reproductive plasticity underlies the resilience of invasive parasites like Varroa.

Eliash, N., Endo, T., Hua, X. et al.
Varroa mites escape the evolutionary trap of haplodiploidy.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-77125-8

Copyright: © 2026 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What Eliash and her colleagues have uncovered is not evolution running backwards according to some predetermined route. It is a lineage modifying the way chromosomes are inherited so that its reproductive system has reacquired an important feature of the ancestral diploid condition. Evolution has no forward gear, no final destination and no prohibition against revisiting an earlier solution when the necessary developmental machinery remains available to be modified.

The discovery also illustrates how evolutionary theory makes otherwise puzzling observations intelligible. Varroa destructor passed through severe founder bottlenecks, reproduces through repeated sibling mating and yet remains capable of adapting to new honeybee populations, changing environments and human attempts to control it. Its functionally diploid males help preserve heterozygosity and maintain a larger effective population size than conventional haplodiploidy would allow. What first appeared to be a paradox becomes understandable when inheritance is examined in evolutionary terms.

There is no suggestion that the mites anticipated their future invasion of Apis mellifera or evolved this system in preparation for it. Natural selection has no foresight. The reproductive arrangement arose through alterations of inherited biology and persisted because, under the circumstances in which the mites reproduced, those alterations helped their bearers leave descendants. When human activity later brought western honeybees into contact with Asian mites and transported infested colonies around the world, that inherited capacity helped make Varroa an exceptionally successful invader.

None of this resembles the creationist picture of separately created kinds furnished with fixed reproductive systems. Even the distinction between haploid and diploid male development—something that might appear to be a fundamental property of an organism—can be evolutionarily remodelled. Nor does the finding support the familiar creationist claim that evolution can only destroy genetic information and produce degeneration. Here, modification of chromosome transmission enables genetic variation to persist despite extreme inbreeding.

It also leaves advocates of intelligent design with the usual moral difficulty. The beneficiary of this ingenious-looking adaptation is a parasite that wounds honeybees, feeds upon their tissues, transmits debilitating viruses and contributes to the collapse of entire colonies. If every effective biological mechanism must be credited to a designer, then so must the mechanism that makes this destructive parasite unusually resilient. Evolution requires no such moral contortion: natural selection is indifferent to welfare and favours the reproductive success of parasite and host alike.

There is a final lesson in the history of Varroa itself. For most of the twentieth century, scientists mistakenly classified this mite as Varroa jacobsoni. Genetic evidence corrected that error and revealed V. destructor to be a separate species. Scientists then assumed that it possessed the conventional haplodiploid reproduction common among related mites; pedigree evidence has now corrected that assumption too. Far from exposing a weakness in science, these revisions demonstrate its essential strength: conclusions remain open to testing, and when the evidence contradicts an accepted account, the account changes. Creationist dogma, by contrast, begins with an unalterable conclusion and requires the evidence to accommodate it.

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