[Federal Register Volume 89, Number 59 (Tuesday, March 26, 2024)]
[Proposed Rules]
[Pages 20927-20928]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-06221]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R4-ES-2021-0092; FXES1111090FEDR-245-FF09E21000]
RIN 1018-BF43


Endangered and Threatened Wildlife and Plants; Threatened Species 
Status With Section 4(d) Rule for Pyramid Pigtoe

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

-----------------------------------------------------------------------

SUMMARY: We, the U.S. Fish and Wildlife Service (Service), withdraw the 
September 7, 2021, proposed rule to list the pyramid pigtoe (Pleurobema 
rubrum), a freshwater mussel, as a threatened species under the 
Endangered Species Act of 1973 (Act), as amended. This withdrawal is 
based on new information we received following publication of the 
proposed rule that indicates the pyramid pigtoe is not a valid listable 
entity under the Act. In 2023, a comprehensive genetic analysis 
throughout the range of the pyramid pigtoe (P. rubrum) and round pigtoe 
(P. sintoxia) mussels concluded that the two mussels are conspecific 
and that pyramid pigtoe is not a valid taxon. Individuals previously 
assigned to P. rubrum are now considered to be P. sintoxia, a wide-
ranging common species. Because we are withdrawing the proposal to list 
the pyramid pigtoe, we are also withdrawing the associated proposed 
rule issued under section 4(d) of the Act.

DATES: The proposed rule that published on September 7, 2021 (86 FR 
49989), to list the pyramid pigtoe as a threatened species with a rule 
issued under section 4(d) of the Act, is withdrawn on March 26, 2024.

ADDRESSES: This withdrawal, comments on our September 7, 2021, proposed 
rule, and supplementary documents are available for public inspection 
on the internet at https://www.regulations.gov at Docket No. FWS-R4-ES-
2021-0092, and some of these documents are also available on the 
Service's website at https://ecos.fws.gov/ecp/species/2781.

FOR FURTHER INFORMATION CONTACT: Janet Mizzi, Field Supervisor, U.S. 
Fish and Wildlife Service, Asheville Ecological Services Field Office, 
160 Zillicoa St., Asheville, NC 28801; telephone 828-258-3939. 
Individuals in the United States who are deaf, deafblind, hard of 
hearing, or have a speech disability may dial 711 (TTY, TDD, or 
TeleBraille) to access telecommunications relay services. Individuals 
outside the United States should use the relay services offered within 
their country to make international calls to the point-of contact in 
the United States.

SUPPLEMENTARY INFORMATION: 

Previous Federal Actions

    Please refer to our September 7, 2021, proposed rule (86 FR 49989) 
for a detailed description of previous Federal actions concerning the 
pyramid pigtoe. We accepted submission of new information and comments 
on our September 7, 2021, proposed rule for 60 days, ending November 8, 
2021.

Finding

    Consistent with section 4(b)(6)(A)(i)(IV) of the Act, we are 
notifying the public that we are withdrawing the September 7, 2021, 
proposed rule to list the pyramid pigtoe as a threatened species with 
an associated rule issued under section 4(d) of the Act (``4(d) rule'') 
(86 FR 49989). The basis for this action is described below.

Background

    It is our intent in this withdrawal to discuss the new information 
identifying the pyramid pigtoe and round pigtoe as conspecific 
(belonging to the same species) that serves as the basis for our 
decision. A thorough review of the life history, ecology, and overall 
viability of what was considered pyramid pigtoe at the time the 
September 7, 2021, proposed rule was published is found in the species 
status assessment report (SSA report) (version 1.0; Service 2021, pp. 
19-36).

[[Page 20928]]

Taxonomy

    Species identification of pyramid pigtoe and round pigtoe, as well 
as between other related taxa, is challenging due to morphological 
similarity and phenotypic plasticity. It is further exacerbated by the 
fact that many species are sympatric (overlapping in geographical 
distribution) (Olivera-Hyde et al. 2023, pp. 2-5). Recent genetic 
studies led researchers to suggest that the pyramid pigtoe and the 
round pigtoe may be conspecific (Inoue et al. 2018, p. 694; Olivera-
Hyde et al. 2023, pp. 8-14), although species experts continued to 
support recognition of the pyramid pigtoe as a valid taxon due to 
morphological differences and a lack of comprehensive rangewide genetic 
information comparing the similar taxa (Olivera-Hyde et al. 2023, p. 
15; Williams et al. 2017, p. 39). Because the pyramid pigtoe and round 
pigtoe are difficult to differentiate, there has been frequent 
misidentification by experts and lumping of the taxa together in the 
academic literature (Olivera-Hyde et al. 2023, pp. 2-5).
    Both the SSA report for the pyramid pigtoe and the September 7, 
2021, proposed rule to list the pyramid pigtoe as a threatened species 
(86 FR 49989) acknowledge the difficulty in identifying the pyramid 
pigtoe. After reviewing the best scientific information available at 
that time, we agreed with mussel experts and found that the pyramid 
pigtoe was a valid taxon (Service 2021, pp. 12-13; see also 86 FR 
49989, September 7, 2021). Since that finding, however, a 
comprehensive, rangewide genetic analysis has been completed comparing 
pyramid pigtoe to round pigtoe, and this information now confirms that 
they are conspecific (Johnson et al., 2024, pp. 16-17).

Review of New Genetic Information

    Prior genetic analyses relied on results taken from individuals 
from portions of species' ranges, resulting in conclusions that were 
limited to only those areas where individuals were collected (Inoue et 
al. 2018, p. 698; Olivera-Hyde et al. 2023, p. 3). The new study uses 
data collected from throughout the ranges of both pyramid pigtoe and 
round pigtoe populations (Johnson et al., 2024, entire). Genetic data 
were successfully sampled from 200 individuals for mitochondrial DNA 
(mtDNA) analysis, 106 individuals for nuclear DNA (nDNA) analysis, and 
176 individuals for genotype-by-sequencing (GBS) analysis across 11 
populations and 22 waterbodies (Johnson et al., 2024, p. 33). 
Mitochondrial DNA and nDNA were used in previous studies but were found 
to be problematic for supporting species delineations in Pleurobema, 
due to potential hybridization and backcrossing effects, resulting in a 
reliance on hard-to-distinguish morphological variation for species 
delineations (Olivera-Hyde et al. 2023, p. 14). The most recent 
analysis incorporated GBS methodologies to address uncertainty in 
assessing whether pyramid pigtoe is a valid taxon (Johnson et al., 
2024, p. 6.).
    The results of the study support the hypothesis that pyramid pigtoe 
and round pigtoe are conspecific based on mtDNA, nDNA, and GBS data 
(Johnson et al., 2024, pp. 13-17). The results of the GBS analysis 
cluster individuals based on geographic location and not by species 
identification based on morphology (Johnson et al., 2024, p. 16). This 
finding is also supported by the results of the mtDNA and nDNA analyses 
and is consistent with the results of prior published findings (Inoue 
et al. 2018, p. 694; Olivera-Hyde et al. 2023, pp. 8-14). The results 
do not support the current morphologically-based species delineations.

Summary of Justification for Withdrawal

    New rangewide genetic information has become available since the 
publication of our September 7, 2021, proposed rule (86 FR 49989) to 
list the pyramid pigtoe as a threatened species with an associated 
section 4(d) rule under the Act. The new information is based on mtDNA, 
nDNA, and GBS data, and concludes that pyramid pigtoe and round pigtoe 
are conspecific. These results support the findings of previous studies 
that were too narrow in scope to make definitive conclusions of species 
delineation. The resulting single species (round pigtoe; P. sintoxia) 
is wide-ranging and common throughout its current range. Because 
pyramid pigtoe (P. rubrum) is no longer considered a valid species, we 
withdraw the September 7, 2021, proposed rule (86 FR 49989) to list 
pyramid pigtoe as a threatened species with an associated section 4(d) 
rule.

References Cited

    A complete list of references cited in this document is available 
on the internet at https://www.regulations.gov and upon request from 
the Asheville Ecological Services Field Office (see FOR FURTHER 
INFORMATION CONTACT).

Authors

    The primary authors of this document are the staff members of the 
Fish and Wildlife Service's Species Assessment Team and the Asheville 
Ecological Services Field Office.

Authority

    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

Martha Williams,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2024-06221 Filed 3-25-24; 8:45 am]
BILLING CODE 4333-15-P